Best engines for Donzi 28ZX / 28ZXO ?!?

[richardoren]

Hi Guys,

Here are the engine choices for the 28 foot ZX / ZXO hulls:

496 Mag B1 375
496 HO B1X 425
500 B1XZ 470
T- 5.0 EFI B1 260 EA
T-350 MAG MPI B1 300 EA
T-MX 6.2 Mag. B1 320 EA
T-377 SCORPION B1 350 EA

Which would you recommend ?

My use will be overseas where gasoline costs upwards of $6/gallon... but the water gets rough so I'd feel safer with a Twin. Plus, them Scorpions sure are tempting, but what do they drink?

Thanks in advance for your help, I'm scouting the ads for one but don't want to have to switch boats after purchase - this one has got to be a keeper.

Cheers,

Richard

[Donzigo]

I like the 425 hp 496 option. Perhap a little slower; but, more economical and less costly on maintenance down the road. The vortec engines are quite reliable.

Good luck.

[undertaker]

I had a 2000 28ZX twin 350 MAGS great performance with those engines IMO the best engine combo for the 28ZX package.

If you are looking for a new 28ZX and opt for the twin 350's Frank C. (Shanghied Again on this board) has a 2005 in stock at a very GOOD price :eek!: give him a call or check out his web site www.typhoonperformancemarine.com. Great guy to talk to and buy a boat from. :yes: Good Luck :biggrin: :biggrin:

If I can help you out in anyway let me know.

Undertaker :cool!:

[Cuda]

I'd go the 6.2's, I don't think the extra 30 hp is worth the money they want for blue engines.

[BUIZILLA]

6.2's

[kkriina]

:sombrero:


if you are worried about gas prices then twin arent the area you want to get into..... But you have to decide what you want, if you want to go as fast as you can then a single wont do it, but it would be cheaper. But you can always modify the 496HO, i have seen them close to 1000hp. :rlol: Or you can always go down to a smaller boat......how about a snail boat?:jestera:

[fasttrucker]

I have a 28zx with single 502.Upgraded motor to over 500hp.The boat was way too slow stock only 65mph.If you go with the 496/425hp you will be sorry! go with the 525hp single.Iam not sure you can still get the hp500.
Life too short to go SLOW! :yes:

[Shanghied Again]

The 28 ZX with Twin 350 Mags would be my choice, The Scorpion package is gone and way to pricey with motors, gasoline. Scorpions need Hi Test. The 6.2 package is a little more expensive then the mags and almost run the same speed 70 mph. Whats nice about the 350 Mags if you ever want to supercharge them in the future you can, whipple makes a nice package.
Do Not go with a single engine with the 28, resale is terrible plus to get better then 70 mph you will need a 525,the 496/HO will only get 62mph, rule of thumb when you are dealing with a boat that weighs over 6000lbs go with twins: you save on gas, you have know drive issues and the boat is much eisier to handle, plus the boat will be more expensive with a single 525 then twin 350 mags.

[richardoren]

I have a 28zx with single 502.Upgraded motor to over 500hp.The boat was way too slow stock only 65mph.If you go with the 496/425hp you will be sorry! go with the 525hp single.Iam not sure you can still get the hp500.
Life too short to go SLOW! :yes:

Hi Fasttruker,

I'll bet that your 500hp rocket sure moves. But here fuel really costs, here's a link to a forum thread about a STOCK 502 Mag in a Rinker, and you'll see what people here say:
http://groups.google.com/group/uk.rec.boats.power/browse_thread/thread/f15c75a15e5fb7a5/b3600417b2fbbde7?lnk=st&q=mercruiser+502+magnum&rnum=2&hl=en#b3600417b2fbbde7

Now don't get me wrong, I'm prepared to spend some bucks on fuel, but would prefer it to cost me $100/hour instead of $200 or $300.

Could you give me an idea of what your approximate GPH is, and on what hull?

TIA.

Richard
(not Rich, though don't I wish)

[richardoren]

I like the 425 hp 496 option. Perhap a little slower; but, more economical and less costly on maintenance down the road. The vortec engines are quite reliable.

Good luck.
HI Donzigo, thanks for wishing me luck as it looks like I'm going to need some. Not to find a good boat, but to buy the right one.

While some of you here may think I'm being hard to please, I'm just going through want others may be sooner than later, trying to figure out how to get Offshore enjoyment with $6/gal gas prices...

This means that the 425hp Horizon might be an option, granted that due to the weight of the boat it doesn't stay too long in the hole eating gas. Also, with rough seas, maybe higher low-end torque would be the ticket with a stroker engine and rounded lobe camshafts and bigger prop(s)? I'd be ready to mod engine(s) if it meant the best of all worlds:
- reasonable fuel consumption
- quick out of the hole
- decent, if not ultimate 75% WOT cruising speed
- safe handling in rough seas

Let me know if you think that the 425HP single can deliver on some of these points.

Thanks!

Richard

[richardoren]

I had a 2000 28ZX twin 350 MAGS great performance with those engines IMO the best engine combo for the 28ZX package.

If you are looking for a new 28ZX and opt for the twin 350's Frank C. (Shanghied Again on this board) has a 2005 in stock at a very GOOD price :eek!: give him a call or check out his web site www.typhoonperformancemarine.com (http://www.typhoonperformancemarine.com/). Great guy to talk to and buy a boat from. :yes: Good Luck :biggrin: :biggrin:

If I can help you out in anyway let me know.

Undertaker :cool!:

Hi Undertaker,

Thanks for the advice, I'll definitely check in with Frank who has apparently already seen this thread, if I choose to go with the 350 Mags. It seems that their 600HP might give them approximately the same performance as a single 500HP engine (given the extra weight). However, I'll have to figure out if the additional fuel consumption is justified by the better rough water handling of twins, and extra safety in case of...

OTHERS here, is 600HP the sweetspot for this Hull? (26 to 28foot Donzis)

Cheers,

Richard

[richardoren]

:sombrero:


if you are worried about gas prices then twin arent the area you want to get into..... But you have to decide what you want, if you want to go as fast as you can then a single wont do it, but it would be cheaper. But you can always modify the 496HO, i have seen them close to 1000hp. :rlol: Or you can always go down to a smaller boat......how about a snail boat?:jestera:

Hi KKRINA,

I can understand your justified humor. True, what is a guy doing in a Donzi forum squeeling about gasoline? :propeller

I may well be inclined to follow your advice, and get a used ZX / ZXO with a single engine, Frank seems to think that they'd come cheap as underpowered in stock form. Then on to hotrodding it. If kept reliable, it actually might cost less in purchase price + mods + fuel than a more expensive twin?

Let me know what you think would be the best candidate.

TIA

Richard

[richardoren]

The 28 ZX with Twin 350 Mags would be my choice, The Scorpion package is gone and way to pricey with motors, gasoline. Scorpions need Hi Test. The 6.2 package is a little more expensive then the mags and almost run the same speed 70 mph. Whats nice about the 350 Mags if you ever want to supercharge them in the future you can, whipple makes a nice package.
Do Not go with a single engine with the 28, resale is terrible plus to get better then 70 mph you will need a 525,the 496/HO will only get 62mph, rule of thumb when you are dealing with a boat that weighs over 6000lbs go with twins: you save on gas, you have know drive issues and the boat is much eisier to handle, plus the boat will be more expensive with a single 525 then twin 350 mags.

Hi Frank,

Thanks for your advice. So far, unless I get a great deal on one with a pair of Scorpions (still need to know how much more they burn than the 6.2s) it looks like Twins 350s or single 500 (or souped up 6.2).

Could you explain the "known drive issues" of singles? Isn't the Bravo One up to snuff?

Thanks

Richard

[Shanghied Again]

The problem you have with a single drive set up is the Bravo 1 can handle to 500hp providing you don't launch the boat also you have to factor in the weight of the boat you are pushing a single drive pushing a 6200lb boat dry. when you put gas gear, people you are looking at 7200lbs, thats a lot of weight for a single drive to handle, I already took out 2 drives in my 26ZX because of Poker Runs

[kkriina]

Sounds like you want speed and would pay for it, twin setup is better for trade in value. lol and its gonna cost more then $100 to run that bad boy. But i would go with the t/6.2l 320hp B1 or higher. scorpions are not worth the extra cost, sure they look great but for 30hp per engine bah, set of good headers can do that. 6.2's make a nice base for upgrades. imco advantage drive would look nice on a 26zx!!!



Good luck bro!

[Mr X]

I am partial to the twin Scorpion package.

[richardoren]

Hi Frank,

I understand how you have been :shocking: by Bravo Ones!

But don't the stronger singles have upgraded Bravos?

- 425 HP 496 Horizon: Bravo 1X
- 470 HP 500: Bravo 1XZ

Are these drives not sufficiently reinforced for their horsepower? Or did you lose the boat in those Poker runs?

[richardoren]

Sounds like you want speed and would pay for it, twin setup is better for trade in value. lol and its gonna cost more then $100 to run that bad boy. But i would go with the t/6.2l 320hp B1 or higher. scorpions are not worth the extra cost, sure they look great but for 30hp per engine bah, set of good headers can do that. 6.2's make a nice base for upgrades. imco advantage drive would look nice on a 26zx!!!

Good luck bro!
Thanks for wishing me luck - I'm in the market for quite a bit of it. :rlol:

I take it that twins will probably deliver more of a punch, but I was sort of hoping that one of these, fitted with a proper drive (dump the upgraded Bravo, Frank?) would possibly give a nice kick while guzzling one third less than twins?
http://img.photobucket.com/albums/v47/richardoren/Mercruiser500EFI.jpg

Is this an UNANIMOUS Thumbs Down for this Single? :confused:

[richardoren]

I am partial to the twin Scorpion package.

Hi Captain X,

Those Scorpions do look indeed pretty and promise some punch.
But at what RPMs is their torque curve? I prefer low-end grunt to high-end HP. Not everyone's preference of course, but big blocks and strokers have their partisans.

- are the Scorpions considerably thirstier than the regular 6.2 liter engines?

- are the Scorpions less reliable? Some here seem to find them "higher maintenance".

Thanks for letting me in on your secrets. :boat:

Richard

[Shanghied Again]

The Bravo 1 is good till about 500hp with a 500 or a 525 I would only use a Bravo XR drive nothing less and thats where the $$$ come in over a stock Bravo 1; With my new motor set up I will be running a Imco Drive to much hp to run through a Bravo. Its those Dang Poker Runs :redface:

[kkriina]

2 of those blue 500's would be real niceeeeeeeeeeeeeeeeeeeeeeeeeeeee.





And dont get the bow rider, cuddy CABIN!!!!!!!!!!!!!!!!!!!!!!!!


Bravo1 is only good for 500hp, imco advantage drives are simply perfect! intergrated hydrallic steering!!!!!!!! man that is some sexy hot boiling ****!! Expensive, but damn!
http://www.imcomarine.com/pages/sterndrives.html

My dream would be to have this drive on a 22zx with 500hp.....:smileybo: <--shes not hot, how about a upgrade?

[daboys]

plenty of power out of the hole and good top end speed (I guess its all relative). The open bow provides lots of excitemnet. I tried a single, not sure the power - I think it was a 496 - the boat was sluggish until it got on plane which took too long for me. If you cruise at 45mph or so the gas bill isn't too bad but when you run WOT it is thirsty but what a rush....... :D

[fasttrucker]

My bravo one is stock except that I changed the lower unit to a low water pickup model and added a drive shower.Also added sidewinder stearing shock system.(telefelx)Which is sposed to make the outdrive more stable resulting in in added speed/safety.I guess Iam pushing my luck its a 1998 unit,still going strong.Iam using about $200 per weekend at $3.10 per gal.

[richardoren]

When at the Red Eye Dock Bar sunday a reporter interviewed us for a story about boating and fuel prices.We said what are you going to do?You just got to pay it.If anyone here reads the washington post and spots it please send me a message,thanks.
Hi Fasttrucker,

I couldn't resist the temptation to quote your other thread - since you were talking about gas prices. Just wondering... what did you tell those reporters? Some guys buy their girl diamonds, so you can figure that fueling a Donzi is quite a bit cheaper? :yes:

How many hours at what speeds per weekend?

[richardoren]

The Bravo 1 is good till about 500hp with a 500 or a 525 I would only use a Bravo XR drive nothing less and thats where the $$$ come in over a stock Bravo 1; With my new motor set up I will be running a Imco Drive to much hp to run through a Bravo. Its those Dang Poker Runs :redface:
Hi Frank,

Thanks for clarifying. I guess this puts some points into the Scorpio package arena: they come with Bravo One XR Sport Master gearcases and drives although they "only" pack 377HP a-piece.

It is increasingly sounding like the Twin Scorpio package is over-engineered for less break-downs under rough treatment. Let me reassure you that I would baby it along, unless certain urges press me on. :smash:

[richardoren]

Hi Kkriina,

Here's my comments & questions:


2 of those blue 500's would be real niceeeeeeeeeeeeeeeeeeeeeeeeeeeee.




Twin 500s like our Admin? (he,s got a portly 38 footer though) ;)


And don't get the bow rider, cuddy CABIN!!!!!!!!!!!!!!!!!!!!!!!!

Why on EARTH not the ZXO ?!?!?

Doesn't it perform up to snuff, or is your's just an aesthetic preference?


Bravo1 is only good for 500hp, imco advantage drives are simply perfect! intergrated hydrallic steering!!!!!!!! man that is some sexy hot boiling ****!! Expensive, but damn!
http://www.imcomarine.com/pages/sterndrives.html


Those IMCOs sure look nice, but the prices make me gasp... maybe I'm not enough of a speed freak yet? Do you need the entire $10k drive or can you just use a top end?

My dream would be to have this drive on a 22zx with 500hp.....:smileybo: <--shes not hot, how about a upgrade?

Nice picture of your pretty Donzi fan, but where I boat they all sunbathe topless. :D

[fasttrucker]

OK,I run a log book so I went upstairs to get it.On the weekend of 6/25 I filled up and put in 73.1 gal at $2.75 per gal.I showed going 7.8 hours...
7.8 div. by 73.1 --is 9.37 gal per hour.I also added up 35.7gal+60gal+72gals to make 167.7gal div by 15.4 hours....10.88 gal per hour.I run fast and slow so thats that.Hope that helps.Somewhere between 9.37+10.88 gal per hour.

[Mr X]

Here are a couple of pics of my 28ZX engines. The Scorpions were built for racing, they are extreamly durable and have tons of acceleration. My boat runs in the mid 80's easily. They are every bit as reliable as the 6.2, they do use about 20% more fuel however.

I dont think you can get a 28ZX with big blocks. Too much weight in the back and the boat was undrivable.... if I remember correctly.

[richardoren]

OK,I run a log book so I went upstairs to get it.On the weekend of 6/25 I filled up and put in 73.1 gal at $2.75 per gal.I showed going 7.8 hours...
7.8 div. by 73.1 --is 9.37 gal per hour.I also added up 35.7gal+60gal+72gals to make 167.7gal div by 15.4 hours....10.88 gal per hour.I run fast and slow so thats that.Hope that helps.Somewhere between 9.37+10.88 gal per hour.

Gee Fasttrucker, it sure is great that you hold such a nifty LOG book. And those fuel numbers look a lot better than I would have guessed. At 10GPH I'd be out only a reasonable amount of $ even at $6.50/gallon. Given an average speed of 30mph I guess that would come to around $2/mile ($1/mile for you lucky guys paying only $3.25/gallon). :yes:
:beer:

[richardoren]

Here are a couple of pics of my 28ZX engines. The Scorpions were built for racing, they are extreamly durable and have tons of acceleration. My boat runs in the mid 80's easily. They are every bit as reliable as the 6.2, they do use about 20% more fuel however.

I dont think you can get a 28ZX with big blocks. Too much weight in the back and the boat was undrivable.... if I remember correctly.
Hi Mr X,

Those pictures are giving me a severe case of "engine envy". http://www.donzi.net/ubb/wink.gif

If I remember correctly, the Scorpions are Mercury 5 racing hand built blueprinted and balanced 6.2 liter engines. Does their extra 20% thirst come from bigger injectors or supercharging? Do they run more fuel per hour at higher speed = close to identical miles per gallon? Not that their added kick doesn't justify some slack at the gas pump. :checkered

[richardoren]

The whole twins burn more argument is pretty much crap in the real world.. The real world is normal cruising, something boats do the majority of the time. So, lets see: My 496HO ZXO @ 45 MPH @ 4000 RPM's, or, my 28ZXO with twins running 45 MPH @ 3000 RPM's???
Hi Scott,

I guess it mostly comes down to how wide open the throttle is... or the throttles are.

One exception might be bigger propping to get on plane extra fast at a lower speed = lower potential fuel consumption at low speed plane?

But who is looking for that... yet - after all gas is still under $10/gal.:rlol:

So I guess that fuel consumption numbers are a NON ISSUE? What really matters is boat usage and how heavy you are with the throttle? Others here, please confirm or disclaim this statement.

Here are some numbers Phil (MOP in the registry) has posted in an ad for a 28ZX with twin 350 MPIs:
Performance Information
Equipped with Twin Mercruiser 350 MPIs as this boat is:

Acceleration

5 seconds 24 mph
10 seconds 45 mph
15 seconds 58 mph
20 seconds 66 mph
Mid-Range Acceleration
30-50 mph 5.4 seconds
40-60 mph 7.3 seconds
40-70 mph 16.9 seconds

RPM vs. MPH
1000- 7 mph
1500- 9 mph
2000- 19 mph
2500- 27 mph
3000- 41 mph
3500- 50 mph
4000- 56 mph
4500- 64 mph
5000- 69 mph

Top Speed at Speedometer - 75 mph
Top Speed on Radar 71.6 mph at 5250
Time to plane - 5.7 seconds
Minimum planing speed - 18 mph
Fuel Economy - At 25 mph 2.5 mpg
At 35 mph 2.4 mpg
At 45 mph 1.9 mpg
At WOT 1.6 mpg
Fuel Capacity - 94 Gallons
Tests Conducted At Sarasota, Fla.


:bonk: Do these numbers look optimistic or realistic to you?

[The Hedgehog]

Just buy a used 28' single. It has already been hit on the resale right. Put in one of the new marine diesels and a nice solid surface drive. There is no way a pair of 6.2's will be even close to that. It will have a nice solid cruise, maintenence costs will be much lower and reliability will be good. Some of the folks in Europe are already doing that.

But don't do that if you plan to resell the boat in a year or two. It will be hard to recoup your cost. At least in the US.


BTW there is no way two lower units can be more efficient than one. They have twice the parasitic drag. Yes I know that this is kind on simplistic but it is basically true.

I have one of those 28' singles and that has well over 500 hours on a single Bravo with no problems. That is not what I would have bought if I was looking at new boats but I let someone else take the hit.

Just remember that I am talking about used boats. If the game is brand new boats and going 70+ then 6.2's are the the way to go

[richardoren]

Just buy a used 28' single. It has already been hit on the resale right. Put in one of the new marine diesels and a nice solid surface drive. There is no way a pair of 6.2's will be even close to that. It will have a nice solid cruise, maintenence costs will be much lower and reliability will be good. Some of the folks in Europe are already doing that.

But don't do that if you plan to resell the boat in a year or two. It will be hard to recoup your cost. At least in the US.


BTW there is no way two lower units can be more efficient than one. They have twice the parasitic drag. Yes I know that this is kind on simplistic but it is basically true.

I have one of those 28' singles and that has well over 500 hours on a single Bravo with no problems. That is not what I would have bought if I was looking at new boats but I let someone else take the hit.

Just remember that I am talking about used boats. If the game is brand new boats and going 70+ then 6.2's are the the way to go

Hi Louisville Boater,

I understand your issue with additional drag. But on this heavy a hull one might argue that a single engine is at the limit of hp production to move it at its design spec speed, which might be closer to 600hp than 500hp?

Furthermore, I thought that most marine diesel engines would be far heavier than gas engines, offsetting some of their torque benefits?

Which single Marine Diesel engine would you recommend for such a Re-Power?

Then comes the issue of the cost of a diesel Re-Power versus the expesne of thirstier consumption in gasoline engines. A fellow where I boat has Twin diesel 750hp engines in his 38' Scarab. Says he gets about 50 gph with it. Sounds better than with gas engines, it was worth it to him.

Like I said earlier in this thread, this boat will be a keeper - and not for resale in the forseable future. So resale considerations can be evacuated as long as it delivers the following:

1. More than the issue of speed, I want to get optimum seaworthiness at a given speed being in the open sea most of the time. That is why I targeted the Donzi 28ZX/28ZXO although folks at the Speedwake forum also recommend the Sunsation 288 for its rough water ride.
:moped:

2. Raw performance comes next, 'cause when I'm not hauling the extended family to secluded beaches I want a fun ride too.
:boat:

3. Keeping fuel use under control is last, although not insignificant with high gasoline/diesel prices in Europe which stand to rise sharply and suddenly in coming years.
:uzi:

[richardoren]

28' and single engines are fine. There are plenty of single engine 28' boats that can scream.

I would be more concerned with the 454 mag than the twin issue. You can modify a single 502 to run in the 70's for about $8k. (maybe a little less depending on what else you want to overhaul) Then you will have one engine and lower unit. The fuel efficiency will be better as well.

It also depends on what kind of boating you are doing. If you are going to be constantly airing it out in bigger water than the twins are probably the way to go. If you are riding around on a lake than you don't need two.
Hi again Louisville Boater,

I hope you don't mind my quoting your post from another thread - it is about the same boat.

I will actually be "airing it out in bigger water" so I guess you would indeed recommend twins?

TIA

Richard

[The Hedgehog]

Hi again Louisville Boater,

I hope you don't mind my quoting your post from another thread - it is about the same boat.

I will actually be "airing it out in bigger water" so I guess you would indeed recommend twins?

TIA

Richard

No problems with the quote.

As for the previous question about wieght, it looks like you are doing some serious homework. There is an outfit out of Oklahoma that is marinizing the 6.5 litre hummer engine. The weight difference is not substantial and efficiency is proven. I can get you their site if you want. There is an active discussion on OSO regarding that topic.

Furthermore, mercruiser is in a joint venture with Cummins to develop diesels to hook up to Bravo's. I don't know the outcome of that process yet but it sounds interesting. I am sure that there must be some merit or else they would not be throwing millions in R&D for this setup. It would be great if someone would do the Duramax but I hear that availability is an issue.

I also believe that Yanmar and Stehr are also in the hunt.

Re the drives, if you plan to air it out you will need to be careful with a Bravo and a high torque engine. Very true. That goes for twins with big blocks as well. A substantial portion of drive failures comes from driving technique. If you want something good and reliable to romp on the the twin small blocks may indeed be for you. It would probably be the easiest thing route to take. You could also look at using an ASD6. It is strong and will will pick up about 10-12% more efficiency. Add that to a more economical engine and hmm. I am sure that you are also familiar with other drives like IMCO, B-Max etc. They do work. Although the 28ZX is on the heavy side, many 27-29 foot boats are raced offshore with single engines.

I am simply thowing out another possible alternative. You should probably do some type of break even analysis. At our current gas prices the maintenance vs cost for mods to repower (including a stronger drive) ect will probably tell you to go to twins. At least for a 3-5 year period. At your cost, a 40-50% fuel savings may tell you to look at alternatives. It will depend on driving style and hours per year of use etc. The diesel/surface drive combo is not new. It has been done on many larger boats by Hustler, Fountain and Donzi. Hustler had one that they used for endurance offshore runs. They would go for distance against Cigarettes. The Cig's would come by at 100 mph while the Hustler would cruise at 70-75. The Cigs would get hot and have to stop and cool off while the Hustler would cruise on. Eventually the Cig's would break something. For high usage situations it is proven. Sort of like the tortus and hair scenario except that 70 mph is not bad. I just have not seen it applied to smaller boats in many cases. It at least warrants consideration.

[Mr X]

Yanmar has had Bravo drives bolted to them for the last 8 years.

My friend has a 22 classic that runs 80 MPH at 9 gallons per hour at WOT.

[richardoren]

Yanmar has had Bravo drives bolted to them for the last 8 years.

My friend has a 22 classic that runs 80 MPH at 9 gallons per hour at WOT.

Hi Captain X,

Is this what you had in mind?


http://www.yanmar.com.au/marine/lp_series/lp_series_lg.jpg (http://www.yanmar.com.au/marine/lp_series/lp_series_lg.jpg[/IMG]g)

It looks like those Yanmars sure are complicated = read expensive to maintain. I would hope the Humvee based engines would be closer to "field maintenance" specs?

The fuel cost benefits could become rapidly eroded by an engine which is expensive to maintain, plus requires more winterization.

Let me know if I've got it all wrong...

[richardoren]

No problems with the quote.

As for the previous question about wieght, it looks like you are doing some serious homework. There is an outfit out of Oklahoma that is marinizing the 6.5 litre hummer engine. The weight difference is not substantial and efficiency is proven. I can get you their site if you want. There is an active discussion on OSO regarding that topic.

Furthermore, mercruiser is in a joint venture with Cummins to develop diesels to hook up to Bravo's. I don't know the outcome of that process yet but it sounds interesting. I am sure that there must be some merit or else they would not be throwing millions in R&D for this setup. It would be great if someone would do the Duramax but I hear that availability is an issue.

I also believe that Yanmar and Stehr are also in the hunt.

Re the drives, if you plan to air it out you will need to be careful with a Bravo and a high torque engine. Very true. That goes for twins with big blocks as well. A substantial portion of drive failures comes from driving technique. If you want something good and reliable to romp on the the twin small blocks may indeed be for you. It would probably be the easiest thing route to take. You could also look at using an ASD6. It is strong and will will pick up about 10-12% more efficiency. Add that to a more economical engine and hmm. I am sure that you are also familiar with other drives like IMCO, B-Max etc. They do work. Although the 28ZX is on the heavy side, many 27-29 foot boats are raced offshore with single engines.

I am simply thowing out another possible alternative. You should probably do some type of break even analysis. At our current gas prices the maintenance vs cost for mods to repower (including a stronger drive) ect will probably tell you to go to twins. At least for a 3-5 year period. At your cost, a 40-50% fuel savings may tell you to look at alternatives. It will depend on driving style and hours per year of use etc. The diesel/surface drive combo is not new. It has been done on many larger boats by Hustler, Fountain and Donzi. Hustler had one that they used for endurance offshore runs. They would go for distance against Cigarettes. The Cig's would come by at 100 mph while the Hustler would cruise at 70-75. The Cigs would get hot and have to stop and cool off while the Hustler would cruise on. Eventually the Cig's would break something. For high usage situations it is proven. Sort of like the tortus and hair scenario except that 70 mph is not bad. I just have not seen it applied to smaller boats in many cases. It at least warrants consideration.

Hi Louisville Boater,

Looks like you nabbed my attention there...

I think it would require mods to the fuel tank etc but this guy looks like the ticket:
http://www.marinedieselusa.com/marine-engine-technicals.html

...but it sure sounds like a UPS delivery van...not exactly a smooth and sexy purr :jestera:
http://www.marinedieselusa.com/marine-engine-mdboatvid.html

What I am wondering is whether one of these in Single engine configuration would be powerful enough to move a 28 foot Donzi - plus if it would be heavy enough to assist wave penetration in heavy seas?
:lookaroun

[The Hedgehog]

However, I would not expect to get 70 mph with that particular engine. I would guess somewhere in the low 60's with a Bravo. It might push close to 70 with an Arneson. Hopefully one of the surface drive guys will speak up. The strong low end torque would result in a nice tractable powerband in heavy seas. I talked to these folks. They told me that it would work fine with a Bravo. It sounded like a bunch of torque through one drive pushing a heavy boat. I would think that with the strong low end torque a beefed up Bravo or a Bravo Diesel Drive would be better. I can't remember how much it cost. I am thinking in the $20m range without any drive mods but don't quote me on that. The mod should be pretty straight forward. At that price you would need to get something discounted for needing a repower.

Doing simple math it will not work unless you figure fuel savings. If you took a well used 28zx you would be at $55m+ pretty quick with the repower. That should buy a mid to low time twin 350. Your fuel savings over a three summers would be approaching $10m (and that is using $3 per gallon at 100 hours per summer). You would also get a nice break on insurance for having a boat with much less horsepower. Once again this is simple math. There are probably some other factors both positive and negative to consider. I will probably put a sharper pencil to it myself for grins.

I have heard about the Yanmar Bravo combo. I heard that something like that was actually put in a Classic 22 by the factory. I heard that the one big pipe got some funny looks. Perhaps that is the one that Mr. X's friend owns. I would like to know more about that myself. I have actually heard that the Yanmar was supposed to be good for about 2000 trouble free hours. I would like to know about that as well.

I would like to know what Merc is going to create. It should be good but it is bound to be expensive.

[The Hedgehog]

Moving along the lake at 65+ mph, throwing a big roostertail yet sounding like the UPS truck. That is pretty funny. Doing that while burning half the gas is even more funny.

[BUIZILLA]

We have a Yanmar pump/injector job in my shop right now with in excess of 8000 hours, it is untouched since new.

JH

[Last Tango]

Fun thread, here. But I need to add my own voice to this. If you are going twins...
I own and happily run a Classic 18 with the MX6.2MPi motor and a Bravo One drive. I researched the heck out of the Scorpion motor before I ordered my boat, then decided against it.
Fact: Scorpions REQUIRE Premium Gas. MX6.2MPi runs on any grade at the pump with no discernable difference in performance between grades used. (allows you to save about 20 cents a gallon per fill up - YOU do the math for a season). Is Premium always available at the marinas you frequent? Using less than Premium in a Scorpion is okay, but the engine management system computers back off the timing to prevent detonation. How much HP do you have now? Using El Cheapo in an MX6.2MPi means you still have 320 HP.
Fact: There are really only TWO horsepower versions of the Scorpion. NEITHER had 377HP. Mercury rated them at 340HP and 350HP. V-drive ski tow boats usually got the bigger HP ones. Depends on where you measure the HP.
FACT: Don't get your hopes up for a new boat with twin Scorpions. Motor is not in regular production anymore.
Fact: With a nice shiny (polished) set of EMI Thunder headers and manifolds, the MX6.2MPi is about the same HP as a stock Scorpion. Set of exhausts plus installation, about $1500. Price of Scorpion motor of the same displacement as the MX6.2MPi, about $7,000 more than the MX6.2 MPi, retail... each.
Fact:MX6.2MPi gets awesome mileage. And all years of production have the full computer and chip diagnostics system. Wanna hook up a complete digital gauge package. No problem. Scorpion?.. ummmm.
The specs on the two motors are VERY similar. Difference is in the crank shaft design, cam, timing, injection sytem, compression ratio. MX6.2MPi can be supercharged as easily as the 350 MAG and starts out with more cubes and better parts. A Bravo One X is a good choice for the drive.

Still can't decide between single or twins? I can't help you there. My choice would be to have the NEXT Donzi ZR package come as a 29ZR with the 525EFI single and 6 Drive, or near equivalent. Whole lotta boats in that class and configuration in offshore racing. Must be something to it...
Plus I had a Z3250 Daytona with twin 454 Mag MPi's. Maintenance? Annual maintenance charge was exactlly the same as my MX6.2MPi, except for one small difference - that was the price PER MOTOR. A $750 annual maintenance becomes $1500 with twins. The big twin motor boat is gone. The single is still here. And I bought the single first, and had both at the same time.

Want twin BIG BLOCKS in your boat. Mercury has from the start maintained that the MX6.2MPi was the actual REPLACEMENT for the 454 series engines. Smaller, lighter, faster...

Okay, I have spent about a bucks worth of my two cents.

[richardoren]

I had the pleasure of speaking with a number of Donzi factory guys at the boat show. I'm like you in the sense that I have a 22ZX and want a 28ZXO. I also thought I would rather have a single motor, the new 525EFI to be exact. I figured that motor with a whipple or a procharger would get me the same power as a pair as a pair of scorpions with less weight and less drag maybe good for 85mph on the right day. Nick Miller one of the VP's at Donzi was nice enough to give me a pass to go for a ride on the new 38ZR, the gentlemen who gave the test rides happen to be the same guys that do the actually testing of the boats with all the different motors and drives and props ect. They told me because of weight distribution the boat actually handles much better with twins and that Donzi was actually thinking about discontinuing 28's with single i/o's. So I've stopped dreaming about blown 525EFI's and now I'm dreaming about blown 6.2's. The stock 6.2's have 320 horse each so the boat should go low 70's no problem, they are capable of supporting the new smartcraft system which is awesome, and for an extra 10 grand a pair of whipple's will turn them into 500hp monsters which should get the boat into the high 80's if not low 90's with some tweaking. If you still want a boat with scopions Perico Harbor Marina has a brand new 2001 28ZX with scorpion's for $79,000 listed in the Dupont Registry, i'm pretty sure the graphics are standard scorpion yellow with blue checkers. Their number is 941-795-2628. I was going to buy it but i decided i really wanted the ZXO. I hope this helps.

I hope Pstorti from the OffshoreOnly Forum doesn't take offense at my unauthorized quote. It seems that Twins might be more compatible with the 28's design?

[richardoren]

However, I would not expect to get 70 mph with that particular engine. I would guess somewhere in the low 60's with a Bravo. It might push close to 70 with an Arneson. Hopefully one of the surface drive guys will speak up. The strong low end torque would result in a nice tractable powerband in heavy seas. I talked to these folks. They told me that it would work fine with a Bravo. It sounded like a bunch of torque through one drive pushing a heavy boat. I would think that with the strong low end torque a beefed up Bravo or a Bravo Diesel Drive would be better. I can't remember how much it cost. I am thinking in the $20m range without any drive mods but don't quote me on that. The mod should be pretty straight forward. At that price you would need to get something discounted for needing a repower.

Doing simple math it will not work unless you figure fuel savings. If you took a well used 28zx you would be at $55m+ pretty quick with the repower. That should buy a mid to low time twin 350. Your fuel savings over a three summers would be approaching $10m (and that is using $3 per gallon at 100 hours per summer). You would also get a nice break on insurance for having a boat with much less horsepower. Once again this is simple math. There are probably some other factors both positive and negative to consider. I will probably put a sharper pencil to it myself for grins.

I have heard about the Yanmar Bravo combo. I heard that something like that was actually put in a Classic 22 by the factory. I heard that the one big pipe got some funny looks. Perhaps that is the one that Mr. X's friend owns. I would like to know more about that myself. I have actually heard that the Yanmar was supposed to be good for about 2000 trouble free hours. I would like to know about that as well.

I would like to know what Merc is going to create. It should be good but it is bound to be expensive.
Hi Louisville,

Going Twin diesels would allow keeping stock Bravo drives, retaining the heavier Twin's seaworthiness in high waves, add the safety of a spare engine in case of storm breakdowns, keep the engine price down (those hammerheads are expensive).

But it may be possible to make some of the fuel savings of diesels with twin gas engines.

Sure, Diesel is much less expensive if you take into account its fuel density, a gallon of diesel packing in more pounds of detonation than its more refined (read "diluted") gasoline counterpart. But Pound per Pound (not Gallon per Gallon) the spread between the two might come from their engine design:

- due to their prevalent free rolling/coasting automotive applications, gasoline engines are designed to provide high rpm horsepower at the expense of low rpm torque.

- due to their prevalent industrial, trucking, and merchant marine applications, diesel engines are designed to provide low rpm torque at the expense of high rpm horsepower.

This means that for obvious reasons, instead of just throwing exponentially greater horsepower at our propellors, we might be well advised to throw more torque at them and get bigger props (ie like wider tires on a race car).

Offshore racing might have precluded the use of diesels in the past due to their poor weight/performance ratio. This is no longer an issue since the advent of Common Rail direct injection and lighter diesel engine design.

But Offshore racing is primarily an advertising vehicle for performance boat builders and especially for *** Marine engine manufacturers ***. One can readily understand that there is more money to be made by simply adapting dated automobile engines to a marine environment than re-tooling factories for new generation diesel engine manufacturing. One option is a milk-cow cash generator, the other is a cost-intensive leap into the unknown.

So nowadays "performance" diesels remain marginal market offerings either from small independent companies, foreign firms with a history of marine diesel manufacturing, or small subsidiaries/joint-ventures of our industry's big players. This means that performance diesels are not price competitive with their gasoline counterparts, reducing the economic logic of optimal consumption/KW.

This can bring some of us, who don't like being milk-cows for unadapted technology and hate feeling the cut of bleeding edge pricing, to look elsewhere for solutions.

There is one midpoint "patch" to current gasoline engine offerings which just might do the trick: turning a high rpm horsepower biased engine into a lower rpm (read: closed throttle) torquey gasoline burner.

A fellow in a newsgroup once suggested that I look into stroker Chevy engines for more low end grunt. Here's his suggestion for an ideal combination of fuel economy and low end torque. It is a5.7L 350 gas engine stroked to 383 and recammed by Ryan's Engines, however, I don't think that these come in marinized boat versions:

Displacement: 383 cu. in.
Carburetor: Holley 750 double pumper
Heads: World Products S/R Torquer, bowl blended
Intake: Edelbrock Performer RPM
Camshaft: Comp Cams Xtreme Energy, with 256/268° of duration, 212/218° of duration @ 0.050 in. lift, and 0.447/0.454 in. lift. (Corrected valve lift with 1.52:1 rockers is 0.453/0.460 in.)
Rockers: Comp Cams Magnum roller 1.52:1
Pistons: cast
Rods: 5.7 in.
Crank: SCAT cast
Distributor: MSD Pro Billet HEI
Timing: 30°
Comp. Ratio: 9.6:1
MAX HP: 338 @ 4800
MAX Torque: 426 @ 3600

Performance engineer Steven Ekdahl gave me this input about such a configuration:

Rich, I was looking at the specs you provided on the 383, I think 30 degrees total advance is too much combined with 9.6:1 compression if you're going to run 89 octane fuel. Also, I would can the 750 double pumper and go with a 750 vacuum secondary. Would work much better on high load situations as found in marine engine. Mechanical double pumpers on a boat engine, is not the way to go. As far as the specs on the hp and torque, your boat is going to fly.

This leads me to examine whether one could just do a top end swap to a stock 5.7MPI using its rounded cams and valvetrain: it wouldn't have quite as much torque as the stroker described above, but the special cams might bring its torque surge down to 3600 rpm or so? Sounds good enough for a re-propping and less thirsty throttle positions.

Flagship Marine Engines http://www.flagshipengine.com/index.htm (http://www.flagshipengine.com/index.htm)
has a surprizingly high torque 5.7L engine - it isn't even a stroker - that puts out 400 lb-ft of torque at 3500rpm. It is still a high rev engine with its max horsepower quoted at 5200rpm which means lots of torque at low throttle settings - nice for marine propulsion. Here are its specs:

57350RJ - 5.7 Litre (350 CID)
350 hp @ 5200 RPM / 400 lb-ft @ 3500 RPM
1 piece seal
9.4 to 1 compression ratio
Vortec cylinder heads

Not many engine details there, but it could be worth checking out if they sell bolt-on heads to use with an existing 5.7L engine?

In any case it might be worth weighing the price/benefit differential between this as a low cost option and switching to a stroked 383 for quite a bit more cash.

It could give Twin Scorpion performance at considerably less fuel consumption, even if propping would need to be painstakingly sorted out. That sure would make my day!
:happy_bi:

[richardoren]

...I have heard about the Yanmar Bravo combo. I heard that something like that was actually put in a Classic 22 by the factory. I heard that the one big pipe got some funny looks. Perhaps that is the one that Mr. X's friend owns. I would like to know more about that myself. I have actually heard that the Yanmar was supposed to be good for about 2000 trouble free hours. I would like to know about that as well...
I think that the 2000 hours trouble-free is using a "continuous use" industrial evaluation => running at 2/3 WOT day and night for that length of time. With the lesser solicitation of our pleasure craft use, this is usually multiplied by 4 - the 8000 hours on the Yanmar in BUIZILLA's shop can attest to this. Many diesel engine manufacturers have charts showing the ratings of each engine depending of their application, with very large durability and price spreads.

[richardoren]

Fun thread, here. But I need to add my own voice to this. If you are going twins...
I own and happily run a Classic 18 with the MX6.2MPi motor and a Bravo One drive. I researched the heck out of the Scorpion motor before I ordered my boat, then decided against it.
Fact: Scorpions REQUIRE Premium Gas. MX6.2MPi runs on any grade at the pump with no discernable difference in performance between grades used. (allows you to save about 20 cents a gallon per fill up - YOU do the math for a season). Is Premium always available at the marinas you frequent? Using less than Premium in a Scorpion is okay, but the engine management system computers back off the timing to prevent detonation. How much HP do you have now? Using El Cheapo in an MX6.2MPi means you still have 320 HP.
Fact: There are really only TWO horsepower versions of the Scorpion. NEITHER had 377HP. Mercury rated them at 340HP and 350HP. V-drive ski tow boats usually got the bigger HP ones. Depends on where you measure the HP.
FACT: Don't get your hopes up for a new boat with twin Scorpions. Motor is not in regular production anymore.
Fact: With a nice shiny (polished) set of EMI Thunder headers and manifolds, the MX6.2MPi is about the same HP as a stock Scorpion. Set of exhausts plus installation, about $1500. Price of Scorpion motor of the same displacement as the MX6.2MPi, about $7,000 more than the MX6.2 MPi, retail... each.
Fact:MX6.2MPi gets awesome mileage. And all years of production have the full computer and chip diagnostics system. Wanna hook up a complete digital gauge package. No problem. Scorpion?.. ummmm.
The specs on the two motors are VERY similar. Difference is in the crank shaft design, cam, timing, injection sytem, compression ratio. MX6.2MPi can be supercharged as easily as the 350 MAG and starts out with more cubes and better parts. A Bravo One X is a good choice for the drive.

Still can't decide between single or twins? I can't help you there. My choice would be to have the NEXT Donzi ZR package come as a 29ZR with the 525EFI single and 6 Drive, or near equivalent. Whole lotta boats in that class and configuration in offshore racing. Must be something to it...
Plus I had a Z3250 Daytona with twin 454 Mag MPi's. Maintenance? Annual maintenance charge was exactlly the same as my MX6.2MPi, except for one small difference - that was the price PER MOTOR. A $750 annual maintenance becomes $1500 with twins. The big twin motor boat is gone. The single is still here. And I bought the single first, and had both at the same time.

Want twin BIG BLOCKS in your boat. Mercury has from the start maintained that the MX6.2MPi was the actual REPLACEMENT for the 454 series engines. Smaller, lighter, faster...

Okay, I have spent about a bucks worth of my two cents.
Hi Mark,

I hope this really isn't your last tango, unless you decided to only dance Waltzes. ;)

Actually in Corsica, there is only regular. But regular in Europe is higher octane than in the USA, so I'd have to do some figuring. I don't even know if they use the same octane rating scales!

Maybe the 6.2 l engines would be mod-able with rounder camshafts. They are famous for their great hp/consumption rate and this could be converted to an excellent torque/consumption rate with different cams and reflashing the engine management computer?

Let me know if you've heard of torque mods for the 6.2s. :cool:

[BUIZILLA]

Maybe the 6.2 l engines would be mod-able with rounder camshafts.
oh boy.....

[richardoren]

oh boy.....
Hi JH,

I take it you are partial to diesels?

Rich

[BUIZILLA]

Hi JH, I take it you are partial to diesels? Rich
not always, I just prefer camshafts with little bumps on them. Those tend to work better.

Jim

[kkriina]

I would put this bad boy in there!!!!


http://www.gce.cummins.com/mce/mce_m11/assets/Fr2970.pdf



HP:660 @ 2300rpm
TOR:1715 @1700rpm!!!!!

WOT: 33gal/hr @ 2300RMP




weighs about 2500lbs


two scorp's weigh about 2400lbs? and do not produce that kinda power.


1715lb/tq you could spin a barn under your boat, there would no such thing of lack of power. Boats require torque, thats what keeps them moving in the water and diesels are made to work and they last longer then gas. A boat moving in water is under a heavy load at all times and require higher RPMS to keep speed up. If your engine is only spinng 1700rpms then there is less wear because its not moving as much which it results in more life.


Ok no bravo can handle this engine but surface drive on a Donzi 26zx would look sweet! Wonder what kind of gearing and prop it would need!!!!




1700POUNDS OF TORQUE BABY!!!!!!

[richardoren]

I would put this bad boy in there!!!!

http://www.gce.cummins.com/mce/mce_m11/assets/Fr2970.pdf


HP:660 @ 2300rpm
TOR:1715 @1700rpm!!!!!

WOT: 33gal/hr @ 2300RMP

weighs about 2500lbs

Two scorp's weigh about 2400lbs? and do not produce that kinda power.

1715lb/tq you could spin a barn under your boat, there would no such thing of lack of power. Boats require torque, thats what keeps them moving in the water and diesels are made to work and they last longer then gas. A boat moving in water is under a heavy load at all times and require higher RPMS to keep speed up. If your engine is only spinng 1700rpms then there is less wear because its not moving as much which it results in more life.

Ok no bravo can handle this engine but surface drive on a Donzi 26zx would look sweet! Wonder what kind of gearing and prop it would need!!!!

1700POUNDS OF TORQUE BABY!!!!!!
Hi Kkriina,
Startin' to recognize you! :beer:

That engine looks like a Poker Run Royal Flush.
The only problem might be a BIG one ... size.
Plus the fact it may cost more than the boat...

I couldn't find its physical dimensions, but with over 10L displacement and that kind of weight I would wager that it may not fit neatly into the 26ZX/28ZX/28ZXO engine bay?

But then again, who really uses those aft sunpads??? :smileybo:

[kkriina]

If i had money to play with, i would creat a highperformance boat using diesels......no questions asked!





And the dimensions(i found on another PDF file)


65.77Lx42.72Wx39.73H

ALL IN INCHES


It is kinda long......... But i think it would take up less room then two 6.2's



There are alot of diesel engines out there and im not quite fimilar with them, but based on what ive read and seen.... Cummins would be my first choice, but ya your probably right, it would cost quite a bit.... But you would be the only 26zx with 680hp diesel under the hatch!!!! LOL that would own so bad!




But if you were to get the twins get the 6.2's not scorps (they use premium) i think someone already said this, and to get there extra power. After your warranty is over, upgrade the engines.... whipples sounds pretty good along with some forged alumium pistons.......man



The diesel sounds better though and you could sell the 6.2' to offset the charge for a diesel.....probably get $50,000 for them.. that will probably buy you your diesel. Then some surface drives would probably run another $20,000.

[richardoren]

Update

Found the dimensions here:
http://www.cmdmarine.com/PDFs/4000080_1104.pdf

It seems that is isn't all that big as I had imagined, given its huge torque numbers.

length is 53.5"
height is 39.7"
width is 42.7"

Here a surface review:
http://powerandmotoryacht.com/engines/0103enginespreview/index11.html

In the boatdiesel.com forums guys are talking about turbocharging them. :yippie:

[richardoren]

Funny we each got different size specs.

Now those numbers you are suggestion are anything but funny.
I expected expensive, but $50 grand for one engine?!? :shocking:

Rich (don't I wish)

[JPR]

Okay guys, we are finally on to something that I may have 1/2 a clue about. I run a fleet of trucks and we have about 9 cummins engines in service, none small enough to fit in the boats that we are talking about, but to make a long story short, I spend alot of time talking to a mechanic who is a cummins specialist. His comment is that you can take the b series cummins (5.9 litres) and get a very reliable, long lasting 450 hp out of it. I can get a list of what is needed , but he indicates that the cost of the mods to take the stock 250 to 450 is about $2,000. Thre are enough of these engines around that you can find used ones in the $4,000 to $5,000 range. The hours that can be put on a diesel engine relative to a gas engine are such that in a recreational boat, a diesel is a once in a lifetime investment. My only concern is the lack of an RPM range. One thought is a 2 speed transmission like an old powerglide. I'm just not sure if they can take the torque.

[kkriina]

Nice, it would surely fit in the 26zx....

That would be awesome.... damn, DONZI OPT FOR DIESELS!!!!!! GRRRR





the reason why i say $50,000.



Brand new 350mag MPI B1 $15,000 plus installation.



The diesel will require custom fabrication to the stringers, new fuel cell, modifications to the transom to acquire a surface drive. And when you look at the cruisers that upgrade the engines there a huge cost.....



HAHAHA i did a search for the cost of the ASD10's and i found a parts list cost for a F/A18 fighter jet......www.navsup.navy.mil/pls/p5star/ url/ITEM/F9FA4E201E823A8CE03400306EF4F03D -



But any try to find the cost i say $20k or more



surface drive on a classic!!!
http://arneson-industries.com/images/Donzi.jpg

[kkriina]

Nice, it would surely fit in the 26zx....

That would be awesome.... damn, DONZI OPT FOR DIESELS!!!!!! GRRRR





the reason why i say $50,000.



Brand new 350mag MPI B1 $15,000 plus installation.


But anyone try to find the cost of a ASD10, i say $20k or more

The diesel will require custom fabrication to the stringers, new fuel cell, modifications to the transom to acquire a surface drive. And when you look at the cruisers that upgrade the engines there a huge cost.....



HAHAHA i did a search for the cost of the ASD10's and i found a parts list cost for a F/A18 fighter jet......www.navsup.navy.mil/pls/p5star/ url/ITEM/F9FA4E201E823A8CE03400306EF4F03D










surface drive on a classic!!!
http://arneson-industries.com/images/Donzi.jpg

[richardoren]

Okay guys, we are finally on to something that I may have 1/2 a clue about. I run a fleet of trucks and we have about 9 cummins engines in service, none small enough to fit in the boats that we are talking about, but to make a long story short, I spend alot of time talking to a mechanic who is a cummins specialist. His comment is that you can take the b series cummins (5.9 litres) and get a very reliable, long lasting 450 hp out of it. I can get a list of what is needed , but he indicates that the cost of the mods to take the stock 250 to 450 is about $2,000. Thre are enough of these engines around that you can find used ones in the $4,000 to $5,000 range. The hours that can be put on a diesel engine relative to a gas engine are such that in a recreational boat, a diesel is a once in a lifetime investment. My only concern is the lack of an RPM range. One thought is a 2 speed transmission like an old powerglide. I'm just not sure if they can take the torque.
Hi JPR,

Thanks for the cool input. :wavey:

As a regular Joe, I obviously would have preferred a simple bolt-in solution of a marinized engine. But the industry is on a gravy train that seems endless in its exponential price rise.

This happens to make your suggestion all the more pertinent. Used engines at $5k a piece are back in regular guy territory. Some of us are handy with a wrench, and for others an engine rebuild is still within financial reach. Double those amounts for Twins, and we're still talking money which doesn't dwarf the purchase price of a used performance boat.

Plus, with today's fuel supply issues (not to mention price), the Cummins B2 is well adapted to Biodiesel:
http://www.agriculture.state.ia.us/biodiesel.html

After testing and field experience, many equipment manufacturers have provided positive warranty position statements including:

Cummins Power Systems, Inc.
What remains to be determined is the fuel consumption of these older less efficient B2s. I'll see what I can find on the web, and post it here. Also, does your Cummins guy build them for low rpm torque, or does he mod them for more higher rpm horsepower?

In any case this sure sounds like a nice alternative to thirsty Scorpions. :cool:

[richardoren]

But how expensive would Surface Drives be?

Here's what they say at Power and Motor Yacht:

...the consensus among surface-drive manufacturers is to expect fuel savings of anywhere from 15 to 30 percent.

http://powerandmotoryacht.com/features/0604surfacedrives/

Apparently a 6 blade prop on an articulated drive would give the best of both worlds? But at what price... :smash:

[richardoren]

Here Ship and Boat International mentions the expiration of the Arneson patent and emerging Italian versions on the market:
http://www.rina.org.uk/rfiles/shipandboat/italy0305.pdf

It looks like more than a year ago the guys at Offshore Only were talking about doing much the same thing as we are:
http://www.offshoreonly.com/forums/showthread.php?t=72489&page=1&pp=20
So I guess we're not as crazy as it looks! Or are we?... ;)

Surface drives may considerably reduce the fuel consumption disadvantage of Twins versus a Single: their props have far less drag and negligeable cavitation, meaning less efficiency losses per kw applied.

This puts Twins back in the running - although it means double the cost for surface drives. The Arneson ASD8 can reportedly be bought for roughly $12K per drive, new with warranty - not a negligeable consideration. But then there are other surface drives out there.

Do any of you know of cheaper surface drives which can handle the torque of a 500hp+ diesel?

[fasttrucker]

Gee Fasttrucker, it sure is great that you hold such a nifty LOG book. And those fuel numbers look a lot better than I would have guessed. At 10GPH I'd be out only a reasonable amount of $ even at $6.50/gallon. Given an average speed of 30mph I guess that would come to around $2/mile ($1/mile for you lucky guys paying only $3.25/gallon). :yes:
:beer:
I think that because my motor has the stainless marine exhaust,victor jr intake manifold,crane cam,blueprinted/balanced,the block was decked,heads were worked......that it runs more efficently at cruise speed resulting in better fuel savings then a stock motor.

[JPR]

What remains to be determined is the fuel consumption of these older less efficient B2s. I'll see what I can find on the web, and post it here. Also, does your Cummins guy build them for low rpm torque, or does he mod them for more higher rpm horsepower?

In any case this sure sounds like a nice alternative to thirsty Scorpions. :cool:

Ed (my cummins guy) is on Holiday for two weeks (hope none of the trucks go down!) but I'll get more information from him when he is back and post it.

[richardoren]

Ed (my cummins guy) is on Holiday for two weeks (hope none of the trucks go down!) but I'll get more information from him when he is back and post it.
Sounds god JPR, keep us posted. :cool:

Meanwhile, the folks at OSO seemed to be impatient for a marine version of the GM Duramax 6.6 l diesel engine which is sparingly offered as an option on sparing few of their trucks:
http://www.gm.com/automotive/gmpowertrain/engines/duramax/
more info here:
http://www.thedieselpage.com/duramax/2006enginenewsrelease.htm

What would be involved in adapting it to marine use with freshwater cooling?

The following advice was given to me by my buddy Steven Ekdahl:

Rich, if your boat is going to be fresh water cooled, there's really not a lot of differences in a marinized engine. Most are minor changes, such as stainless steel freeze out plugs, bronze lined intake manifold, which you could do without. Heavy duty oil pan to resist rusting out which I would recommend. Stainless steel pump which I'm not so sure I would get it if I was paying for it. So easy to change, not sure if it's worth the upgrade. Being a mechanic, I might look at things differently. The stuff that's hard to change, always better to go overkill. The bearings are the same in a cast water pump and the stainless water pump, if you keep them both painted and cleaned, can't really see why one would outlast the other. In raw water cooling in salt water, now you've got problems. Intake manifold, water pump, oil pan, you name it, freeze out plugs, you need it all and then some...

Any further ideas of what would be involved in adapting the Duramax to marine use with freshwater cooling?

[richardoren]

Regarding swapping stock Bravos for higher output rated surface drives, there are indeed several makes and models. However, to my present knowledge only Arneson makes a simple "bolt-on" replacement kit option (for their model 6) with gearing suitable for diesel torque:
Upgrade the power rating of your ASD6/1721 drive unit with our New HD gear upgrade. Available in 1.32:1 and 1.56:1 ratio's, the gear up grade increases the power rating to over 750 lbs of torque.

Kit description:
http://arneson-industries.com/bravo_to_arneson_conversion.htm

So it is looking increasingly feasible and almost cost-effective to mod a Gasoline/Bravo Donzi into a Diesel/Arneson Donzi. George Desmond did his 18 footer before the kit was available, and much of his work could have been spared. http://www.donzi.net/tech/DonziArneson.htm

The ease of fitting these drives is leading me to look more closely at Diesel engines designed to bolt directly onto Bravo drives. Funny, both the new engine and the new drives will need to connect to a virtual item - the deleted Bravo. :lookaroun

[richardoren]

I hope nobody sues me for quoting this 2002 estimated pricing from boatdiesel forum:

Section: Cummins:QSM Series Topic: Cost of QSM11 580hp Subject: QSM-11 $$$ Name: Tony Athens [email (http://boatdiesel.com/BDR/Forums/SendMail.cfm?EUID=7603JE46404EB45EBE7E64A2A0604044 1&AUID=0201J446408060441&MESID=F29822)] MORE... (javascript:popUpCenteredWindow('http://Boatdiesel.com/PersonalPage.cfm?CFApp=3&TEUID=0201J446408060441&','640','600','yes')) Date: October 18, 2002 09:09 PM Viewed: 744 times For comparison purposes you could assume street pricing for a QSM-11 535 bobtail w/ std analog gages, harnesses a few other goodies is about $32500 here in S. Calif.. Add about $6500 for the 580/635 HP versions and another $500 for the 660HP version.... Transmission options will range from about $7500 to $10,000 depending on the type/make of gear and a few other things.. Digital instruments run about $1400 ea and "C-Cruise" about the same per engine.........Hope this helps...................Tony
At least it would be a single engine configuration. :chillpill

- - - - - - - - - -
Not so rich Rich

[richardoren]

Here's a fellow selling a 34' SeaRay Amberjack with twin PowerStrokes:

http://www.boat-world.com/boatads/1141352381.html

His ad sports this claim:
* Fantastically economical! Documented 12-14 gph

[NYStockboy]

So ahh, what boat are you going to buy?

[richardoren]

So ahh, what boat are you going to buy?
Hi Stockboy,

I'm going to scout out a used twin 5.0L or 350MPI Y2000 to Y2004 28ZXO with indifferent hours but a clean cockpit and hull. The drives will probably be Arneson 6 surface kits with upgraded gears.

The real question remains, which diesel to marinize - Duramax 6.6LLY, PowerStroke 7.3 or * your suggestion *.

Having lost two relatives in the past 48 hours, I'll be signing off this thread for a time. Thanks for adding any suggestions for my return.

----------
Rich
2005 Mustang GT convertible

[richardoren]

To add to the controversy, this was posted by Camelot Mike at rv.net:
"That rating of light duty or medium duty also has to do with the average life span of the engine 240,000 miles for a duramax, 140,000 for a 7.3 liter powerstroke, 250,000 for a 6.0 liter powerstroke, 300,000 for a 12 valve cummins 5.9 and 400,000 for a 24 valve cummins 5.9..."

[richardoren]

Just buy a used 28' single. It has already been hit on the resale right. Put in one of the new marine diesels and a nice solid surface drive. There is no way a pair of 6.2's will be even close to that. It will have a nice solid cruise, maintenence costs will be much lower and reliability will be good. Some of the folks in Europe are already doing that.
But don't do that if you plan to resell the boat in a year or two. It will be hard to recoup your cost. At least in the US.
BTW there is no way two lower units can be more efficient than one. They have twice the parasitic drag. Yes I know that this is kind on simplistic but it is basically true.
I have one of those 28' singles and that has well over 500 hours on a single Bravo with no problems. That is not what I would have bought if I was looking at new boats but I let someone else take the hit.
Just remember that I am talking about used boats. If the game is brand new boats and going 70+ then 6.2's are the the way to go
Hi Big Green,

You know I am already hot on the trail of an Arneson kit. What remains to figure out is the best - highest torque wiht lowest consumption - marine diesel out there. There is one that Sunsation now offers on the Donzi 28ZX/ZXO rival, the Sunsation 288 mentioned in this quote from their forum:

Sunsation now added a Diesel Power Option. ( post 1 of 3)
From: sunsation.com
http://www.sunsationboats.com/forum...hread.php?t=562
I have been asked to let everyone know that Sunsation Powerboats has now added Diesel Power Options to the following models:
288
288 Mid Cabin Open Bowm
32 SS
and the all new 32 SS Mid Cabin Open Bow.
Two V8 Diesels are available:
300hp w/ 514 FT LBS of torque
and also a 330 HP Version
Price wise the diesel engines are a little more than a 496 Mag/HO and substantially lower in price than the HP525 EFI engine option.
The Torque numbers for the diesels are similar to the HP600 SCI engine.
One of the most important considerations in the past has been the weight of Diesel engines. The weight of a 496 Mag/HO with Bravo X or XR is about 1,200 and the diesel engines mated to a Bravo drive are nearly identical - maybe a few dozen lbs lighter.
The on-line configurator spreadsheets have been updated to include the two new engnes options on the 288, 288 MCOB, 32 SS and 32SS MCB.
- jeff
It sounds like it's an older GM Duramax, I'd go bonkers over a newer marinized LBZ version with monster torque, the Arneson can handle up to 750ftlbs. Has anyone here heard of a place that mods them for boats? Oh well, I figure I'll google around and see what I can dig up. :cool:

Richard

[CosmoKat]

Fun thread, here. But I need to add my own voice to this. If you are going twins...
I own and happily run a Classic 18 with the MX6.2MPi motor and a Bravo One drive. I researched the heck out of the Scorpion motor before I ordered my boat, then decided against it.
Fact: Scorpions REQUIRE Premium Gas. MX6.2MPi runs on any grade at the pump with no discernable difference in performance between grades used. (allows you to save about 20 cents a gallon per fill up - YOU do the math for a season). Is Premium always available at the marinas you frequent? Using less than Premium in a Scorpion is okay, but the engine management system computers back off the timing to prevent detonation. How much HP do you have now? Using El Cheapo in an MX6.2MPi means you still have 320 HP.
Fact: There are really only TWO horsepower versions of the Scorpion. NEITHER had 377HP. Mercury rated them at 340HP and 350HP. V-drive ski tow boats usually got the bigger HP ones. Depends on where you measure the HP.
FACT: Don't get your hopes up for a new boat with twin Scorpions. Motor is not in regular production anymore.
Fact: With a nice shiny (polished) set of EMI Thunder headers and manifolds, the MX6.2MPi is about the same HP as a stock Scorpion. Set of exhausts plus installation, about $1500. Price of Scorpion motor of the same displacement as the MX6.2MPi, about $7,000 more than the MX6.2 MPi, retail... each.
Fact:MX6.2MPi gets awesome mileage. And all years of production have the full computer and chip diagnostics system. Wanna hook up a complete digital gauge package. No problem. Scorpion?.. ummmm.
The specs on the two motors are VERY similar. Difference is in the crank shaft design, cam, timing, injection sytem, compression ratio. MX6.2MPi can be supercharged as easily as the 350 MAG and starts out with more cubes and better parts. A Bravo One X is a good choice for the drive.
Still can't decide between single or twins? I can't help you there. My choice would be to have the NEXT Donzi ZR package come as a 29ZR with the 525EFI single and 6 Drive, or near equivalent. Whole lotta boats in that class and configuration in offshore racing. Must be something to it...
Plus I had a Z3250 Daytona with twin 454 Mag MPi's. Maintenance? Annual maintenance charge was exactlly the same as my MX6.2MPi, except for one small difference - that was the price PER MOTOR. A $750 annual maintenance becomes $1500 with twins. The big twin motor boat is gone. The single is still here. And I bought the single first, and had both at the same time.
Want twin BIG BLOCKS in your boat. Mercury has from the start maintained that the MX6.2MPi was the actual REPLACEMENT for the 454 series engines. Smaller, lighter, faster...
Okay, I have spent about a bucks worth of my two cents.
Your "facts" are not correct.
The 377ci Blue Scorpion was rated by Mercury to be a full 377 HP.
There are also more than two versions of Scorpions produced as well.

[richardoren]

Just a notion, maybe they have different flywheel vs. prop horsepower numbers? :umbrella:

Richard

[CosmoKat]

377 HP??
330,340 (Black)
350 (Blue)....
Look again,
Taken DIRECTLY from the Mercury Marine web site:
Scorpion 377 - 377 HP
Specifications
HP: 377
kW: 294
Full Throttle RPM Range: 4800-5200
Displacement Liter/CID: 6.2/377
Bore & Stroke (in): 4.00 x 3.75
Bore & Stroke (mm): 102 x 95
Compression Ratio: 9:1
Cylinder/Configuration: V-8
Alternator Amp: 65
Alternator Watt: 917
Fuel System: MPI
Ignition System: Digital
Fuel Requirements: 92 Posted Octane (R+M)/2 (98 RON)
Drive Unit: Bravo One, Bravo One XR (standard with dual water pick up or optional with low water pick), Bravo One XR w/ITS, Bravo One XR Sport Master (Standard or Short), and Bravo One XR Sport Master (Standard or Short) w/ITS.
Drive/Gear Ratios: Bravo One XR/Bravo One XR Sport Master (Standard and Short) - 1.26:1, 1.35:1, 1.50:1
Length (in/mm): 37/940
Width (in/mm): 29/737
Height (in/mm): 20/508
Weight (lbs / kg): 969/441
Warranty: 1-Year Ltd. for Recreational Boating/3-Year Ltd. Corrosion
CARB Star Rating: 3
Features & Benefits
Balanced and blueprinted, multiport injected V-8 produces 400 foot pounds of torque.
Specialty engine components, including a high-lift hydraulic camshaft, stainless steel intake and exhaust valves, balanced forged-steel crankshaft and lightweight aluminum alloy pistons, enhance power and torque throughout the engine's operating range.
MEFI 3 Electronic Control Module digital ignition system features advanced electronics for more precise fuel and spark control along with better top-end throttle response.
Powerful 65-amp/917-watt alternator provides dependable starting and additional power for operating electrical accessories.
A one-piece serpentine belt system requires less horsepower to drive engine accessories.
Water-cooled and insulated fuel system helps keep fuel temperatures down and greatly reduces potential for vapor lock with today's fuels.
Comes standard with the 1.36:1 or 1.50:1 gear ratio Bravo One drive. Bravo One XR drive also available.
Both Bravo One and Bravo One XR drives are available with a low-water pickup or dual-water pickup gearcase housing.
Bravo One XR Sport Master drives with 1.26:1, 1.35:1, and 1.50:1 gear ratios also available.
The Bravo One XR Sport Master gearcase (Std. and Short), available on selected Bravo One XR drives, reduces drag for enhanced overall boat performance in select applications.
Integrated Transom System (ITS) available with Bravo One XR and Bravo One XR Sport Master drive options.
New engine oil drain line enhances ease of changing oil.

[richardoren]

Hi Guys,

Here's an update.

BigGreen and others here and elsewhere have agreed that plunking a modern common rail diesel isn't a bad idea for a powerboat. Especially if you want loads of propeller twisting torque at economical low rpm engine speed.

To give such a project a fighting chance, it is important to not do anything stupid. This is why I am enlisting the help of folks at the Diesel Page who know the GM Duramax like the back of their hand.

Another advantage is that one of them already put a 2004 Duramax into a Corsa offshore boat. This was the article that mentions it:

LLY Duramax 6600 Marine Diesel
Our marine diesel project included installing an 2004 LLY Duramax 6600 in a 1983 26' Corsa offshore race boat. The engine is mated to a Borg-Warner Velvet Drive transmission and a Mercruiser Super Speedmaster III drive. Working through the electrical/electronic issues for such a conversion was perhaps the most daunting, but this may be the first privately owned marinized Duramax 6600.

I am especially interested in the steps they took to marinize it as well as how they solved the wiring and EEC settings. Considering that most Donzis mate what were initially automotive gasoline engines (Mercruiser=Ford) to Bravo drives, I don't expect any problems in mating an automotive GM diesel to an Arneson "Bravo to Arneson" conversion kit. A direct drive is indeed better suited to the massive torque of this engine, 650ftlbs in its stock version.

Thanks to any here who may have had experience marinizing engines, or for any links or contacts to professionals who are knowlegeable in this field.

Richard :beer:

[Mr X]

Great info Cosmo, I scanned this directly from my owners manual. Notice the very first line of the specs....PROPSHAFT HORSEPOWER.......377HP

[HeavyP]

Here's a really nice one with 2 of those that's for sale.

[richardoren]

Here's an interesting boat being sold by Custom Marine with 4 (yes, four) 300hp Mercruiser 7.3 Navstar V-8 diesels. These are obviously Ford Powerstrokes which have been marinized. Far better than the overly tweaked 6.0L more recent PowerStrokes, not to mention a far cry better than the part aluminum GM Duramax corrosion monsters.
http://www.offshoreonly.com/esvon/page-226.html

http://www.custommarinesales.com/classifieds/index.php?page=out&id=13

Seems these might be a very nice repower option for a ZX with blown engines: higher torque + half the fuel consumption = more beer money + more time to drink it! :cool:

[D byrd]

Hello,

I have one you might cosider. 2003 28zx (200) hours that can be verified by my mechanic or indepedent survey. Like new condition, always dry storage inside, cover, all service records, new tri axel trailer custom built for step hull, latham hydrolic steering, motors , Bravo drives and wiring like new. Interior very good and original. Never damaged or repaired.
She is a head turner and sounds very intimidating. If you have intrest i'll foreward photos.

Thanks D
(910) 599-7594

62k