The amazing DP

[Morgan's Cloud]

Well , do I have your attention now Randy ? :biggrin.:

First off I'd like to add my voice to the many before me who have thanked Big Grizz for his help. He is a tremendous resource to the board .

It was a bit of a well kept secret for the last 12 months or so but the outcome may be of interest to all of the detail oriented technophobes here.
When I finally re-launched the St Tropez last year after it's complete and total rebuild / repower I was horrified at its new 'manners' , or more appropriately , the total lack of !
It was a complete pig ...no , worse , a BEAR .
It was so bad that I hated driving it , and instead of making up for 5 years out of service I barely put 25 hours on it and didn't even put it over this summer.

When I repowered I assumed that the DP unit would be massive overkill on a light 19' boat , so I went with the single prop unit , Volvo's newest the SX-A. The engine is the 5.7Gi , Volvo's counter to the Merc 350MAG .
Even though I finally had a working front fuel tank to help as 'ballast' the bow was so light that it was a constant battle keeping the boat on the water , there was real potential for a blowover !
It wouldn't track in a straight line even in calm weather .. don't even talk about a slight breeze with a broken water surface.
The boat heeled to port as soon as you jabbed the throttle from a fast idle and once on plane you had to maintain port tab to keep it level.
Unfortunately the second you met an oncoming wave the bow would rise slightly and the boat would come crashing down on the flat of the port bottom.

Always porpoising even in corners, the trim couldn't even approach neutral which exacerbated the prop torque.
Turns were a hair raising experience in both directions with the boat bucking , kicking and slamming through them all .
Trying to maintain a straight course at cruising speed with any breeze whatsoever was impossible and I was constantly adjusting the trim tabs to compensate .

What had happened to my baby ?

I know from this site that many a boat has been tamed with the 'prop treatment' from Randy so I PM'd him and arranged a prop to try out.
I would assume that he sent me what he would have considered to be the optimal starting point , I believe it was a Turbo 1 .
Well , the boat might have been marginally smoother and the exhaust note was a tiny bit different (through the leg) but otherwise , no different .
One prop test , out about $500 and still no different. I was very skeptical that a prop was going to fix this and after much rationalising I arranged for Doug Russell in Worcester to send me a DP to test out .
Well , I'm just back from a 2 week break and I did have a day that was suitable for testing. We put it on the trailer and took it to a ramp nearby and over I went.

As soon as I put it in gear I knew something was going on...
I doesn't even hunt at low speeds any more ! The transformation is just amazing , I couldn't believe it . My baby is back .
The feeling of 'security' is fantastic .. turns in either direction are smooth and predictable , no more heeling to the port side , hell , I didn't even touch the tabs during the test and there was a fair breeze blowing too .. the boat didn't fall into the wind when running abeam to it ...
To say that I'm happy would be an understatement.
It wasn't cheap but I couldn't sit back and leave it like it was and chances are that I could have easilly spent $5000 plus on prop testing and still not seen any improvement ..

Oh , by the way , besides the very interesting fact that this was a real life test on the SAME boat not two 'identical' boats from the same manufacturer but with different power packages , there is one other interesting bit of data ..
The old SX-A 1.51:1 gears swung a 21" prop at just about dead on 5000 rpm. The boat was so out of controll that I was unable to gps it , but the speedo which is dead accurate from 0 to 31 mph (that's as high as I was able to gps test it last summer) showed a comfy 60 .
The DPS-A has a 1.95:1 ratio and swings an F8 propset (whatever that is :bonk:) at 4700 .... The speedo is showing 62 + ....... pretty cool huh ?

Now lets eee if I can attach a few pics to make this post interesting ......:biggrin.:

[cutwater]

I am drooling over this one... I have wanted a DP for so long for the Minx, at some point I will have to do it. Good for you for taking drastic action. That looks fantastic and now it handles well, too. Congrats! Any more pics of the boat you can post?

[BigGrizzly]

I am really happy for you. I know how you love this boat. I am still a little at a loss, the prop should have helped. Like I have always said every boat is a little different. I do know the DP does solve a multitude of problems. We did try to save some money but it wasn't meant to be. The good part is you have a boat that is nice and is a keeper. I am glad you kept at it. It will be worth it in the long run.

[Ghost]

Interesting stuff. I have often wondered why more people don't repower Donzis with duoprops. When I have heard complaints about handling, whether here, in published reviews, whatever, most of the things I heard sounded like things a duoprop might cure.

I can imagine everyone here stuffing a bar of soap in a sock and beating me senseless for even saying this, but it seems logical to me.

(I seem to recall a period when Donzi offered Volvo as well as Merc drives, no, but I don't think I've heard more than about two people on the site talk about having Volvos.)

I'm curious what people think about the pros and cons of duoprops for boats like the Classics or other Donzi single engine setups 25' and under. Again, I'm not saying what is better--I don't know. I am just asking. But I always thought if I were going to have a 22 Classic, a Volvo 420HP big block with the high-speed duoprop drive (can't recall the desingator anymore) would be an ideal set up.

Comments are welcome. I am donning a helmet...

[CHACHI]

TONY SPORER, WE NEED YOU.

Ken

[cutwater]

But I always thought if I were going to have a 22 Classic, a Volvo 420HP big block with the high-speed duoprop drive (can't recall the desingator anymore) would be an ideal set up.

DPX... and I want one...


TONY SPORER, WE NEED YOU.

Ken

This Tony?

"1996 22' Classic
Volvo Penta 7.4Gsi/DPX
bone stock 71.8 gps mph"

not bad :wink:

[Conquistador_del_mar]

Well , do I have your attention now Randy ? :biggrin.:


What had happened to my baby ?

I know from this site that many a boat has been tamed with the 'prop treatment' from Randy so I PM'd him and arranged a prop to try out.
I would assume that he sent me what he would have considered to be the optimal starting point , I believe it was a Turbo 1 .
Well , the boat might have been marginally smoother and the exhaust note was a tiny bit different (through the leg) but otherwise , no different .
One prop test , out about $500 and still no different. I was very skeptical that a prop was going to fix this and after much rationalising I arranged for Doug Russell in Worcester to send me a DP to test out .
Well , I'm just back from a 2 week break and I did have a day that was suitable for testing. We put it on the trailer and took it to a ramp nearby and over I went.

As soon as I put it in gear I knew something was going on...
I doesn't even hunt at low speeds any more ! The transformation is just amazing , I couldn't believe it . My baby is back .
The feeling of 'security' is fantastic .. turns in either direction are smooth and predictable , no more heeling to the port side , hell , I didn't even touch the tabs during the test and there was a fair breeze blowing too .. the boat didn't fall into the wind when running abeam to it ...
To say that I'm happy would be an understatement.
It wasn't cheap but I couldn't sit back and leave it like it was and chances are that I could have easilly spent $5000 plus on prop testing and still not seen any improvement ..

Oh , by the way , besides the very interesting fact that this was a real life test on the SAME boat not two 'identical' boats from the same manufacturer but with different power packages , there is one other interesting bit of data ..
The old SX-A 1.51:1 gears swung a 21" prop at just about dead on 5000 rpm. The boat was so out of controll that I was unable to gps it , but the speedo which is dead accurate from 0 to 31 mph (that's as high as I was able to gps test it last summer) showed a comfy 60 .
The DPS-A has a 1.95:1 ratio and swings an F8 propset (whatever that is :bonk:) at 4700 .... The speedo is showing 62 + ....... pretty cool huh ?

Now lets eee if I can attach a few pics to make this post interesting ......:biggrin.:

I'm glad to hear that the DP made such a positive difference! When you virtually eliminate steering torque, the boat can handle so much better overall. Bill


Interesting stuff. I have often wondered why more people don't repower Donzis with duoprops. When I have heard complaints about handling, whether here, in published reviews, whatever, most of the things I heard sounded like things a duoprop might cure.

I can imagine everyone here stuffing a bar of soap in a sock and beating me senseless for even saying this, but it seems logical to me.

(I seem to recall a period when Donzi offered Volvo as well as Merc drives, no, but I don't think I've heard more than about two people on the site talk about having Volvos.)

I'm curious what people think about the pros and cons of duoprops for boats like the Classics or other Donzi single engine setups 25' and under. Again, I'm not saying what is better--I don't know. I am just asking. But I always thought if I were going to have a 22 Classic, a Volvo 420HP big block with the high-speed duoprop drive (can't recall the desingator anymore) would be an ideal set up.

Comments are welcome. I am donning a helmet...

I will be restoring a 27' Magnum sport starting this winter. One of the first things I decided was to go with a single engine and Bravo III drive for better handling so I would not have to install external steering. I am figuring on about a 500HP engine to get the speed I am after which the drive should be able to support. When I first dreamed up this project, I thought it was a little radical, but I have since learned that it works in practice. I will never get radical speeds out of the setup, but I should have a great cruiser on our relatively large lake (Lake Texoma). I will eventually be able to report the results. Bill

[Morgan's Cloud]

A few more thoughts...
Cutwater ... Probably won't be able to get any decent photos of the boat untill later next spring ... Although I could temporarily set up the interior and climb a tree to get a decent shot :tongue:
I wonder about going through the effort to change to a DP unit if your boat already handles OK with a single prop unit. Bear in mind , in my case it was a total resto / repower . I just asked for the 'wrong' outdrive when I put together my package !
Funny thing is that before the resto , I ran this thing for nearly 20 years with a 351/Alpha setup and it had no issues at all.
Maybe this all stems from the fact that the new engine is so much more potent.
When you think about it though , I would guess that our small boats with high power to weight ratios are perfect candidates for the DP unit.
Remember , the unit I have doesn't bear too much resemblence to Volvo's first DuoProp that was introdcued in 1982 . You know.. the units that were responsible for the 'you loose at least 10 MPH' reputation :wink:
Ghost ... When you say you don't hear of many people here using Volvos , I presume you mean the DP units ? In that case , yes . I can only think of 2 others , only one is the high perf DPX and there was another St Tropez that had a B3 installed with a turbo Yanmar.
Otherwise , a large percentage of the pre -82 or so classics were Volvo 250's and 270's.
Randy , after 21 years + with this thing , I think we're joined at the hip ..
Even though it was a total mess when I had it delivered in April 1987 , I knew it was a keeper !

[CHACHI]

DPX... and I want one...



This Tony?

"1996 22' Classic
Volvo Penta 7.4Gsi/DPX
bone stock 71.8 gps mph"

not bad :wink:

Yes, that Tony.

Ther is another board member, McDonzi, who also has a big bolck with a DP hangin' off the transom.

Ken

[Morgan's Cloud]

Bill , have you investigated wether Merc actually offers a 'higher performance' range of B3 props ?
I can tell you first hand , the VP propset I'm running bears no resemblance to the Merc B3 props at all .
Of course you know that I have the 502 B3 in the Magnum , but we never ran the boat before we restored it so we don't know what benefits the B3 provides for it. If it is however , like what I've just experienced in the St T , well we made a good choice then !
Steve

[Morgan's Cloud]

[QUOTE=BigGrizzly;480238] Like I have always said every boat is a little different./QUOTE]

This is very important to remember, I hope no-one overlooks it .

[Ghost]

Ghost ... When you say you don't hear of many people here using Volvos , I presume you mean the DP units ? In that case , yes . I can only think of 2 others , only one is the high perf DPX and there was another St Tropez that had a B3 installed with a turbo Yanmar.

Otherwise , a large percentage of the pre -82 or so classics were Volvo 250's and 270's.

Exactly, yes, I was not specific enough-I meant Volvos with DP units. Thanks.

One other question--am I losing it or did Donzi (for some time in within the '88-'97 range maybe) offer both modern Volvos and Mercs? I would swear I dropped by my local Donzi dealer and saw both available on several occasions, but maybe I'm smoking crack. (Regardless, even if they did, it sounds like very few took them up on the Volvo option.)

Last, I'm probably missing something simple, but does anyone know why Donzi doesn't offer the Classics with the Bravo 3 option, even if they don't work with Volvo? (Can you special order it? Hard to imagine you couldn't but not seeing it on the website makes me wonder...) Does top end suffer or something? I'll be the first to admit I know very little about real high-performance engines and drives, and though I hear a lot about lots of other projects here, the silence on counter-rotating setups is pretty deafening, making me wonder. (Of course, the two comments I have heard about DPs have been *extremely* positive, making me wonder even more why more don't do it.)

Regards,

Mike

[Ghost]

I will be restoring a 27' Magnum sport starting this winter. One of the first things I decided was to go with a single engine and Bravo III drive for better handling so I would not have to install external steering. I am figuring on about a 500HP engine to get the speed I am after which the drive should be able to support. When I first dreamed up this project, I thought it was a little radical, but I have since learned that it works in practice. I will never get radical speeds out of the setup, but I should have a great cruiser on our relatively large lake (Lake Texoma). I will eventually be able to report the results. Bill

Cool--I'm interested to see how it turns out for you. The efficiency of a single over twins is what, maybe 20% or so in HP? The weight savings is going to be about a half ton, right? Admittedly, nowhere near the cubes of twins, but I wonder how it will compare, say, to a pair of 300HP small blocks for top end.

(If I say the word "bow-thuster" will I get stoned to death? Now that I think about it, is it in any way unsafe to put a bow thruster on a performance boat, given the speeds at which you might stuff the nose? If there's a problem there, anyone have a rule of thumb about what speed is too much? 60? 70? ...)

Regards,

Mike

[f_inscreenname]

A bow thruster on a performance boat? I would think it would take to much of a beating at speed and maybe a little to much odd pressure on the bow but what do I know.
I just read this thread for the first time. Morgan’s Cloud I have a question and I hope you will be honest. No judgment from me but I have to know. You say you picked up 2 or 3 mph and some handling over your last set up. On your old set up did you do any prop testing to help the handling? Left and right hand props? I ask because my boat is a “bear” with a right hand prop on it (enough that it broke a steering cable) but with a left it’s like it has power steering from start to WOT. But like said all boats are different.
Now here is the real question. How much did it cost for those couple mph? Motor and DP are not cheap.

[zelatore]

Cool--I'm interested to see how it turns out for you. The efficiency of a single over twins is what, maybe 20% or so in HP? The weight savings is going to be about a half ton, right? Admittedly, nowhere near the cubes of twins, but I wonder how it will compare, say, to a pair of 300HP small blocks for top end.

(If I say the word "bow-thuster" will I get stoned to death? Now that I think about it, is it in any way unsafe to put a bow thruster on a performance boat, given the speeds at which you might stuff the nose? If there's a problem there, anyone have a rule of thumb about what speed is too much? 60? 70? ...)

Regards,

Mike

Your boat is what - 28'? That's a great size for a BB single and duo-prop. And I think many here would tell you (yes, it's arguable) that Volvo makes a better dual-prop drive than Merc.

As for a bow thruster....Oy! What are we going to do with you??

I've never seen one in a performance boat. Heck, I've rarely seen them in boats that small. I know it's been done, both aftermarket and OEM. You'd need to find room for a 6" tube, the motor, and an extra battery all in the bow. I suppose you could do without the battery, but that would mean running some serious cables the length of your boat, and it would be easier to run smaller cables for charging and a small gp24 battery close to the thruster motor. That's also a bit of weight in the very front of the boat.

The fastest boat I've driven with a thruster was a 28 Four Winns with twin 5.0 Volvos. About 47 mph. It was an aftermarket installation, and made no noticeable impact on the boat, but then again it was far, far from a performance hull.

I hope you've got a pocket full of sheckles if you're thinking about installing a duoprop drive and a thruster. Those two will make a blower look cheap.

[Ghost]

Your boat is what - 28'? That's a great size for a BB single and duo-prop. And I think many here would tell you (yes, it's arguable) that Volvo makes a better dual-prop drive than Merc.

As for a bow thruster....Oy! What are we going to do with you??

I've never seen one in a performance boat...

The fastest boat I've driven with a thruster was a 28 Four Winns with twin 5.0 Volvos. About 47 mph. It was an aftermarket installation, and made no noticeable impact on the boat, but then again it was far, far from a performance hull.

I hope you've got a pocket full of sheckles if you're thinking about installing a duoprop drive and a thruster. Those two will make a blower look cheap.

Appreciate the thoughts, all good info.


But I feel compelled to clear up a couple things. :)

"I swear it's not for me."
I was only asking about the bow thruster in the context of people considering putting larger single engines into bigger boats that might have had twins in the past (in this case, Bill's Magnum 27 with a single BB and a duoprop). I can imagine tight maneuvering in the wind might be difficult for some with that size boat and a single. (Of course, "this never happens to me.")
The minute I thought about the possibility of a thruster in a performance boat, it struck me that it could be pretty bad to come down off a wave with a little sideways inclination at 70mph with a bowthruster cutout to snag, hence my curiousity if anyone has such experience.
It's not an issue for me anyhow, and I am not considering any such mods. My Nova Marine (basically the same hull as a Donzi 7-Meter) is a skoche under 25 feet, with a pair of small blocks and inboards with v-drives and rudders. Old technology, but she pivots like the dial on Barry Eller's new phone.
Who needs a thruster on a 28-foot boat with twins?! (Even a chunky Four Winns shaped like an acorn?!)
"I did not have sex with that woman..."
Regards,

Mike

[zelatore]

Who needs a thruster on a 28-foot boat with twins?! (Even a chunky Four Winns shaped like an acorn?!)


That would be one of my clients who pretty much put every possible addition he could on a little Four Winns. Thruster, gen, air and heat, grey and black water tanks, full canvas, TWO gps's and chartplotters, 4KW radar...and more.

Just out of control crazy stuff.

He traded it and moved up to a 42' Carver with twin diesels, bow and stern thrusters, and single lever electronic controls. This was still not enough, so he had us add a cockpit helm station and then a wireless remote so he could control the transmissions and thrusters from anywhere...even the dock. When I installed it and started testing the system, I kept walking further and further away to see what sort of range I could get. I eventually was standing up on shore still moving the boat in and out of gear in it's slip half way down the dock. I swear you could have driving the thing around the marina like a giant R/C toy....

BTW, all that was because he has 'concerns' about docking.

[Tony]

TONY SPORER, WE NEED YOU.

Ken

I absolutely love the DPX on my 22' Classic. An E4 propset (the highest pitch of the three choices; E2, E3, & E4) and the stock 385 propshaft hp puts me at 70 mph in almost all conditions.

Good out of the hole, strong mid-range pull, and true "ride-on-rail" handling thanks to internal hydraulic steering. Zero porpoising, and zero prop torque...quite different than my Ski Sporter! Plus, with the drive designed to handle up to 600 hp, I am counting on a long and productive life for this drive.

Dave MacDonald (mc donzi) has my boat's twin, I'm hoping to join him and the Lake Muskoka gang next summer in Canada.

:beer:

[onesubdrvr]

I absolutely love the DPX on my 22' Classic. An E4 propset (the highest pitch of the three choices; E2, E3, & E4) and the stock 385 propshaft hp puts me at 70 mph in almost all conditions.

Good out of the hole, strong mid-range pull, and true "ride-on-rail" handling thanks to internal hydraulic steering. Zero porpoising, and zero prop torque...quite different than my Ski Sporter! Plus, with the drive designed to handle up to 600 hp, I am counting on a long and productive life for this drive.

Dave MacDonald (mc donzi) has my boat's twin, I'm hoping to join him and the Lake Muskoka gang next summer in Canada.

:beer:
Tony,

You are running the steepest prop set, but the drive is good to 600hp,....

If one were to increase horsepower to 600, what would happen with the props? I mean, it seems that if you're at 5200 RPM now, at 425hp, and go to 600, that the propset is no longer good, so what would you do?

Just curious - I'm a fan of these drives.

Wayne

[Conquistador_del_mar]

Bill , have you investigated wether Merc actually offers a 'higher performance' range of B3 props ?
I can tell you first hand , the VP propset I'm running bears no resemblance to the Merc B3 props at all .
Of course you know that I have the 502 B3 in the Magnum , but we never ran the boat before we restored it so we don't know what benefits the B3 provides for it. If it is however , like what I've just experienced in the St T , well we made a good choice then !
Steve

Steve,
No, I have not even checked out the props. The Bravo III fell in my lap for $1000 with the entire transom assembly, rams, etc. so I couldn't turn it down. It needs a couple pieces welded, but I figured at the price, I could buy whatever is needed to get it going. Until reading this thread, I thought the B3 could handle more power than the Volvo Penta DP. It is such a long way away from needing power that I might change direction before then. Thanks for the response. Bill


Cool--I'm interested to see how it turns out for you. The efficiency of a single over twins is what, maybe 20% or so in HP? The weight savings is going to be about a half ton, right? Admittedly, nowhere near the cubes of twins, but I wonder how it will compare, say, to a pair of 300HP small blocks for top end.

(If I say the word "bow-thuster" will I get stoned to death? Now that I think about it, is it in any way unsafe to put a bow thruster on a performance boat, given the speeds at which you might stuff the nose? If there's a problem there, anyone have a rule of thumb about what speed is too much? 60? 70? ...)

Regards,

Mike

Mike,
Yes, I figure at least 1000+ lbs weight savings going with a single. I think I will end up at around 65MPH with the 500HP and B3, but I will have to find out when it is all done. My guess is that it will end up being around the same top speed as with a pair of 300HP SBCs. Bill

[BUIZILLA]

a DP is underrated... :angel: personally, I think there is some public paranoia or reluctance to use them... in my mind, it's a no brainer... I have never understood why the Volvo unit wasn't better accepted, but maybe it was only the lack of VP's marketing coverage to spread the word, EVERYBODY knows the Volvo DP is a far superior unit to a BIII...

[Donziweasel]

I am kinda curious like Wayne is. If you have 375 hp with the highest pitch available, how do you prop it with 600 hp?????

Hmmmmm........Duoprop on a Critter.......Not this year, but someday????

[onesubdrvr]

I am kinda curious like Wayne is. If you have 375 hp with the highest pitch available, how do you prop it with 600 hp?????

Hmmmmm........Duoprop on a Critter.......Not this year, but someday????

Think smaller,.... about 6' smaller ;)

Wayne

[Tony]

Tony,

You are running the steepest prop set, but the drive is good to 600hp,....

If one were to increase horsepower to 600, what would happen with the props? I mean, it seems that if you're at 5200 RPM now, at 425hp, and go to 600, that the propset is no longer good, so what would you do?

Just curious - I'm a fan of these drives.

Wayne

Good question...and I have no idea how to answer it!

Forest Coile in FL has two DPX's hanging off his Magnum, but I don't know how much hp he pushes thru them.
Forest is very knowledgeable about these drives.

Another guy with experience is over on OSO, his boat is called "Batboat", and his forum name is C_Spray.
The boat is 28' long, 540 ci, 600 hp, DPX-A drive, 92 mph best.
Maybe they created customized prop sets or something?

:beer:

[Tony]

In this oso thread (http://www.offshoreonly.com/forums/general-boating-discussion/196029-how-about-batboat.html) about Batboats, C_Spray says this;

There were only two Swedish-built 28's imported into the US. The first was a blue/burgundy boat with fore-and-aft race seating brought in in 1993, later equipped with a canopy and raced in 1996 (7?) as the yellow "Rain-X" boat in A (then later AX) class. As far as I know, Bill _______ still owns in in the Sarasota area. This was B-28 Hull #1. My boat (Hull #5) was imported in December 1994 as a silver boat with red trim and a half-enclosed full pleasure interior. Both boats were brought in by Volvo Penta as demonstrators for the then-new DPX drive. As far as I know, both hulls were built by a Scandanavian yard named "Batbygaarna", specializing in racing sailboat hulls. Mine is vacuum-bagged and fully foam-cored, including the bottom. US-made boats are solid bottoms.

Unless your boat has a "Batbygaarna" certficate laminated into the front bulkhead of the engine compatment, it's not Swedish. The last time I spoke with the builder/former owner of your boat, he told me that he had bought a bare hull from Armada (now defunct) and finish/painted/rigged it himself. It won its class at the LOTO shootout at least once.

[Ghost]

Good question...and I have no idea how to answer it!

The boat is 28' long, 540 ci, 600 hp, DPX-A drive, 92 mph best.
Maybe they created customized prop sets or something?


This is a purely academic thought, but what about customizing a gearbox?

I don't know squat about the Volvo E series propsets.

The F series propsets are the most common in my experience, and they run from shallow to steep, from (at least) choices "F2" to "F9", lots more than the 3 choices for E listed in the thread above. I can't tell you the exact pitch of each F series prop, but I am looking at some tables from Volvo that I used back in the late '90s when I was doing some shopping. The tables show speed ranges for various engines and drive ratios, when coupled with F2 through F9 propsets.

The fastest of these is the 7.4 GSi with the 1.68:1 drive ratio, because it has the highest factory top end RPM range: from 4800-5200 (The 8.2 tops out at 5k). In the Volvo tables, this translates to roughly 79-87MPH with an F9 propset. I don't have any data on slip, or any other mitigating factors, and I don't know if the chart assumes a certain amount of slip or if it simply a theoretical maximum based on RPM, gear ratio, and the pitch of the prop.

Dunno if the E series propsets were intended specially for the high-performance DPX drive, or if you can use Fs on that. The "typical" run of the mill duoprop (a DP-S I think, at least until the newest drives came out in the last couple years) will take F series props, and it certainly appears from Volvo's tables that these were intended to cover some reasonably high-performance applications.

Maybe with some digging you can find this stuff on their website. I spent a lot of time hunting in the late 90's and at one point they had PDFs with all of these tables available for E series, F series, and several others.

FWIW,

Mike

[Morgan's Cloud]

Exactly, yes, I was not specific enough-I meant Volvos with DP units. Thanks.
One other question--am I losing it or did Donzi (for some time in within the '88-'97 range maybe) offer both modern Volvos and Mercs? I would swear I dropped by my local Donzi dealer and saw both available on several occasions, but maybe I'm smoking crack. (Regardless, even if they did, it sounds like very few took them up on the Volvo option.)
Last, I'm probably missing something simple, but does anyone know why Donzi doesn't offer the Classics with the Bravo 3 option, even if they don't work with Volvo? (Can you special order it? Hard to imagine you couldn't but not seeing it on the website makes me wonder...) Does top end suffer or something? I'll be the first to admit I know very little about real high-performance engines and drives, and though I hear a lot about lots of other projects here, the silence on counter-rotating setups is pretty deafening, making me wonder. (Of course, the two comments I have heard about DPs have been *extremely* positive, making me wonder even more why more don't do it.)
Regards,
Mike
You may be thinking of that period when OMC owned Donzi and they were putting the Cobra/King Cobra drives on the boats . There was a time in the ownership when OMC had to use up 'old stock' and they were producing some boats with Mercs and the Cobra units. The Cobra unit was the result of a Volvo/OMC liason and to some , it may have seemed to be a Volvo unit.
The B3 isn't considered a 'performance' unit so it's hardly surprising that you don't find it on boats like ours ....
One notable exception that I touched on recently though .....
That Lipship Cig 20 (with its huge price tag) comes with a B3 ... I never had any comeback when I brought this up a while back ! hmmmm
BTW , I frequently tell people that smoking crack is probably cheaper than my kind of boating ... hahaha :banghead:

[Morgan's Cloud]

a DP is underrated... :angel: personally, I think there is some public paranoia or reluctance to use them... in my mind, it's a no brainer... I have never understood why the Volvo unit wasn't better accepted, but maybe it was only the lack of VP's marketing coverage to spread the word, EVERYBODY knows the Volvo DP is a far superior unit to a BIII...
I completely agree... I think a lot of it goes back to the introduction of the FIRST DP unit.
Circa 1982 everyone was into making their Merc/ Alpha packages as fast as they could , they couldn't give a toss about handling then
.
Along comes Volvo with a unit that looks like an oversized hand blender , that has all the hydrodynamics of an Amana 22 cubic foot upright refrigerator and that WAS slower boat for boat than an Alpha drive and it didn't take long for the stigma to get firmly attached !
Old habits die hard eh ? That's why I pointed out that the DPS-A bears virtually nil similarity to the original DP.
No matter what the 'stock' package , single prop or DP , Volvo is miles ahead of Merc in terms of engineering and build quality , always has been.
Unfortunately for the US 'domestic market' Volvo is probably seen as an 'imported product' and don't forget , you can't trick them out like a Merc and go fast ....! :biggrin.: :biggrin.:

[Morgan's Cloud]

Dunno if the E series propsets were intended specially for the high-performance DPX drive, or if you can use Fs on that. The "typical" run of the mill duoprop (a DP-S I think, at least until the newest drives came out in the last couple years) will take F series props, and it certainly appears from Volvo's tables that these were intended to cover some reasonably high-performance applications.
FWIW,
Mike
According to my Volvo stuff , the DPX only uses the E series props.
To the untrained eye they do look the same as the F series , but I think the difference might be in the gearcase diameter of the DPX.
There is an aluminium propset range that covers the F series too.
I might just consider a set as my 'spare' .......
Steve

[TXDONZI]

I just bought 2 DPX-R's a transom shield a rear E3and a set of E4's from C_Spray off of the OSO site. They should be here today as a matter of fact. If you are running E4's you must have a lower with 1.78 or maybe a 1.59 drive ratio. Once you step up to bigger hp you would want to change to a 1.47 ratio lower unit to get the RPMs down from what I understand the E4's are some what equal to a 29-30 pitch prop and the others are equal to lower pitchs. Hopfully I will see next summer how all this DPX stuff works. I will be running it on a 1980 20' Kona hull with a BBF 429, next witer I plan to do a rebuild and possible do a 521 or 545 blower motor but only once I see how this boat will handle hopefully over 60-65 before I push it any further.

Tt

[TXDONZI]

They do not list the DPX-600 or the 1.47 ratio drive on the prop selection chart but you can see in the DPX-600 literature they do exist.

40914

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[Lenny]

One notable exception that I touched on recently though .....
That Lipship Cig 20 (with its huge price tag) comes with a B3 ...

The two that were in Kentucky at AOTH this year I thought both had Blackhawks ??? The Red boat and the Blue one...

[BigGrizzly]

Actually one of the cigs had a TRS on it it was raffed up next to Hotshot and Steve.

[MOP]

I did not read many of the posts, I love dou prop drives. When the first Volvo's came out we got them on our Grady Whites, on that hull it was faster all the way around, I know that is not true of all hulls! Mid range with a same HP single running along side showed the dou to be running a couple of hundred RPM slower yet both topped out a 5K with the single being just a tad slower. We also noticed less trim tab was needed on the dou's, also like mentioned above great manueverabilty and -0- steering torque. As most know I tried a BH drive on my 22, from the bottom up to about 4K RPM it was great truly handled like a sports car. It would haul a bunch of people as a few at 1K found out, I absolutely loved everything about the drive except top end was not there. The BH topped high 50's, a swap to a Bravo no other changes put me @65.5 with my mild 383.

[Morgan's Cloud]

Hey there Phil ,
Actually , you were only one of three that knew about this issue I had ...
I thought that I'd just point out something here that I believe should be corrected ...
On more than one occasion here a member has referred to the subject of 'steering torque' and how the DP unit eliminates the problem ..
Nearly all new marine engine packages now have power steering which is what eliminates the problem of 'steering torque'.
The DP unit eliminates 'Prop torque' which is what was causing my problems .
Early on, someone else couldn't understand what my issue was and kept saying that if I had power steering the problem would be taken care of because when their eyes read ' prop torque' their brain saw 'steering torque'....

[MOP]

Hi Steve yes you have it right about prop torque, but I feel all power steering does is mask it by providing power assist. A dou can do without Power steering, I know this as I drove one of our clients boats quite a distance with a blown steering hose. The lack of effort was amazing, for economy sake why use the HP to power a not needed pump!

[Morgan's Cloud]

A bow thruster on a performance boat? I would think it would take to much of a beating at speed and maybe a little to much odd pressure on the bow but what do I know.
I just read this thread for the first time. Morgan’s Cloud I have a question and I hope you will be honest. No judgment from me but I have to know. You say you picked up 2 or 3 mph and some handling over your last set up. On your old set up did you do any prop testing to help the handling? Left and right hand props? I ask because my boat is a “bear” with a right hand prop on it (enough that it broke a steering cable) but with a left it’s like it has power steering from start to WOT. But like said all boats are different.
Now here is the real question. How much did it cost for those couple mph? Motor and DP are not cheap.


Oops , almost forgot to answer this .... no I'm not coy ... haha

The apparent increase in speed was a bit of a surprise and was never my goal. It was the outright terrible handling that had to go. I never tried different rotation props .. Never even entered my mind to be honest. When I hear stories like yours I sometimes wonder if there is also an issue with the motor/outdrive being perfectly centred ... If that could infact cause a problem like you had ....

As for cost .. are you sitting down ....?
I have no idea what the 'trade in value' will be on the original SX-A ... especially if they start whining that it was run in salt water :nilly:
but the installed cost on the boat for the DPS-A was $9000 .
If I was over there with you guys it would have been a whole bunch less but freight and import taxes (who says we're a tax haven :mad:) make a huge difference out here .
(did I mention how much we've benifitted by the dropping oil prices ? Gas is now only US$6.41 a gallon !)

This actually demonstrates what a 'bargain' a complete engine/drive/trans assy package is ... Maybe I should have bought another one , complete, and only kept the outdrive :biggrin.:

So , at the end of the day , if I've seen an increase in top end, that's really nice too , but I just wanted to have a nice controllable boat again !

Steve

[Tony]

Here's another "Batboat" thread, in case anyone is interested:

http://www.speedwake.com/upload/showthread.php?s=&threadid=21038&highlight=dpx

[Tank]

Hi Morgan's Cloud
Good to here you got it working and sorry to here it took the DP to do it I know it means more money! Typical bout just like a lady wants the good stuff ha ha.
Hope you are enjoying it I still have not got mien done.
Had one bad year last year. But that means this one will be better.
Brian

[Morgan's Cloud]

Hey Brian ,

Glad you're still here .

Have you made much progress since we last spoke ?

Another St T showed up here late last year and I have a feeling that we'll be hearing from Dennis again very soon now that he's back on shore (I believe)
His is reportedly the last ST T built (under special circumstances I think)

Yes , I'm very relieved to have sorted out the major handling issue I had , now maybe I can use the thing this summer.

Pity the remedy was so costly but the way things were going I just could'nt believe that a simple prop change was going to fix it.

Steve