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View Full Version : Fast 22C experts, I need help



miike
01-31-2013, 12:48 PM
I'm putting in 600hp this spring. I have stock bennetts and a King Cobra that I would like to keep. I'm willing to spend the money on a custom bracket for steering just to keep it (which is prob cheaper than a bravo swap still.)

Do I need longer tabs? What steering should I get. I've got time to wait for used for a few months and will buy new if there is nothing available. Aside from making the steering bracket and dropping the motor in, I will be doing this by myself. I have installed tabs before, I can fill small holes with resin etc. Also I will install silent choice.

Any advice welcome.

Thank you DONZI.net!

RockyS18
01-31-2013, 12:57 PM
Check out the Bennett ST16 tabs. Pretty much plug and play since you already have Bennetts.

VetteLT193
01-31-2013, 01:08 PM
Hard to say on the tabs because the KC will be a different setup. Dr. Dan I think had an HP500 with a KC, he might be the guy to talk to. Most of the guys running fast have shorty drives. I ran my brother's boat enough to know that it didn't need tabs ever. Only used them when it got rough and were running slower to throw the bow into the waves to make the ride better.


Have you considered spending a bit less on the engine, going for 500-ish HP and putting money into a drive swap?

From what I hear the KC will be a better power handler but I have to imagine you'll be leaving quite a few MPH on the table with a deep KC.

miike
01-31-2013, 01:34 PM
I already bought the motor, but I got a screaming deal. Under 4k for a new solid lifter 502.

I run mostly on Lake Washington in Seattle which is 35 miles long and a mile wide. There is boat traffic on nice days in the summer and some of the bigger yachts kick up large wakes. I usually can see them and slow down for those if I am going fast, but I usually don't open up if it's choppy out. I use my tabs for a nice 45 mph cruise in choppy stuff. When I'm at 50+ I retract the tabs and when I'm playing around jumping waves I don't use tabs unless I need to to keep one side down.

If I don't need to upgrade the tabs I'm all for saving the money. If it's scary at 75mph without the tabs I will just go ahead and get it done. Never been 75mph in a boat before so I don't know. Also, it would be really lame if I installed the steering and planned to do tabs the next year and then found out I needed to move the steering to get the tabs in.

I don't need to squeeze out every last mph. There is no one to race on Lake Wa. I'm sure 75 will be plenty fast for my guests and myself.

undertaker
01-31-2013, 02:07 PM
Since Dr. Dan rarely gets on this site and I run with him ALL the time, I will kind of speak on his behalf:smile: He has a HP500, king cobra drive, no steering, and runs 82-85 all day long. He does not use his tabs at all if anything he keeps them parellel with the bottom of the boat and still runs 82-85. He always says when he gets his big boy pants and runs his tabs all the way up he will actually see what his boat really does:hyper:

He did buy a custom bracket for steering for the King Cobra, he got it from Madpoodle it was a little bit of cash but is a sweet setup. He will be putting Zieger steering on this spring or early summer hopefully. Not sure if Madpoodle has any more or can hook you up with a bracket shoot him a pm on the other site...

IMO your King Cobra will be fine with the HP, and as far as losing some speed with the deeper drive I am still not sold on that fact mainly because of the numbers Danny runs with his setup compared to the other guys with similiar bravo set ups....

Hopefully Danny checks in on this post, he has lots of knowledge on running these boats as he was one the first ones to put a HP500 in his boat with a King Cobra....I talk to him daily so I will let him know about your post.

Good luck keep us posted....:propeller:

Undertaker with a slow red 22 classic :):):sombrero:

miike
01-31-2013, 02:12 PM
The motor will run real high rpm, so I can stick with a lower pitch that will be easier on the drive when I'm cruising around. I'm thinking 27 Mirage. I like how the boat handles now with a 23 Mirage.

undertaker
01-31-2013, 02:17 PM
I believe Dr. Dan runs a 26P TXP turbo prop, he could turn a bigger prop for sure he just hasn't tried on yet, however he has them in his arsenal to be tried:propeller:

gcarter
01-31-2013, 02:35 PM
FWIW, Bravos don't like a lot of RPM.......
Stick w/the KC.

Carl C
01-31-2013, 06:15 PM
Stick with the Bennetts for now, put in the engine and see how she runs. Full steering is nice but tricky to put on your drive I guess.

JayZ
01-31-2013, 09:45 PM
Stick with the Bennetts for now, put in the engine and see how she runs. Full steering is nice but tricky to put on your drive I guess.

I think what you do is remove the raw water pump cover assembly, impeller and wear plate, put some studs in then install a custom steering plate to attach the rams to. I guess you either cut or remove the plastic drive cover so that you can then attach the rams to the custom plate.

---Does this sound about right?

You then install an auxiliary raw water pump and pickup which isn't all bad since the impeller is now obsolete.


...seems a fair amount of work and money for a drive that as nice as it may be is kind of becoming obsolete ...or I guess it will be if and when you break it and yessir even though I haven't got mine running yet ( year behind schedule) I have thought about this a bit.

biggiefl
02-01-2013, 12:42 AM
Miike...what were you running originally(engine(hp), drive ratio, rpm, prop, speed)? I run a stock 330hp through a bravo with a 23 mirage and on a good day see 65 on the GPS(4800-4900rpm) but not sure engine is 100% stock but I think it is(opinions?). I think 600hp would fetch you WAAAYYYY more than 75 with a 27" mirage....more like 85+ with a 28-30 lab? Keep us posted on how this works out but I also agree on both things: 1) you need external steering over 70mph. 2) keep the stock tabs until you think you need otherwise. At full tilt boogie, most tabs are up 100% anyways.....mine are over 45-50mph for the most part. Then again at certain speeds in smaller boats you NEED a k-plane to keep the boat planted. Again drive it first.

PS...does'nt a stock 496HO(425) run 75mph? If so a 600 is crazy hp. I'm happy with 65 with a 7' beam :)

yeller
02-01-2013, 01:56 AM
If you're fine with the tabs you currently have, you will be fine with the tabs and more hp. Generally speaking, the faster you go in these boats, the less tab you need.

I need A TON of tab in my boat....more than most, yet as I go faster, I need less tab.

Now, going fast on Lake Washing Machine can be scary with any length of tab. Lots of confused water on that lake.

Ghost
02-01-2013, 01:59 AM
Not sure how yours is set up but some folks who've done big power like that in a 22C have strongly suggested beefing up the glass and maybe installing a cradle for the motor. There's a not-too-old thread somewhere with lots of specifics...

miike
02-01-2013, 07:02 AM
Miike...what were you running originally(engine(hp), drive ratio, rpm, prop, speed)? I run a stock 330hp through a bravo with a 23 mirage and on a good day see 65 on the GPS(4800-4900rpm) but not sure engine is 100% stock but I think it is(opinions?). I think 600hp would fetch you WAAAYYYY more than 75 with a 27" mirage....more like 85+ with a 28-30 lab? Keep us posted on how this works out but I also agree on both things: 1) you need external steering over 70mph. 2) keep the stock tabs until you think you need otherwise. At full tilt boogie, most tabs are up 100% anyways.....mine are over 45-50mph for the most part. Then again at certain speeds in smaller boats you NEED a k-plane to keep the boat planted. Again drive it first.

PS...does'nt a stock 496HO(425) run 75mph? If so a 600 is crazy hp. I'm happy with 65 with a 7' beam :)

I ran the 330hp 454 with a King Cobra, which is 1.43 (I haven't messed with props for a while so that might be wrong), with a 23 Mirage that I had cut down and added a little cup back into so that it would run 4750. I think my fastest ever was 67mph. I got this motor because it was a great deal, don't really need 600hp, just always wanted to repower with a solid lifter motor and all the machine shops wanted $10k+ to build one and this was sitting complete so I bought it.

I don't go fast usually. I'd be willing to try the 26 turbo if another KC boat is running it into the 80s. Anyone know how to get a hold on Madpoodle? I tried to PM him on S+F yesterday.


Do I need to replace the helm with the Zieger kit? There's one for $2500 and one for $3400 on CPperf. The $3400 has a helm kit.

Thanks

Carl C
02-01-2013, 08:09 AM
Yes, you need a new helm and a special block-off plate to cover the holes, part # 1003000. If you specify a 120 cc helm you will stay at 3 turns or less lock to lock. The helm that they usually include can get you up to 5 turns I've been told. A b*tch at the dock.

You can contact MadPoodle through the only other Donzi forum.

http://i763.photobucket.com/albums/xx275/CARLC222/Pictures085.jpg

MDonziM
02-01-2013, 08:43 AM
Look thru some of the repower threads. When I repowered 5 yrs ago and my 94' had rot in the stringers and "shelves". While the engine is out check everything with a moisture meter. If its all ok, I would still beef up the bottom (either extra glass or additional stringers) and fabricate some bigger/ better engine mounts.

Full steering is a must, can't help with a kc drive. Tabs don't matter from my experience except maybe how fast they move. I had double ram bennetts with a single pump and they were slow. I have bennett 12x12's that should fit right into your transom mounts, if you want them I'll send them to you for a donation to the site or something.

What are your eng specs? To get 600hp from a 502 must have an aggressive cam and high compression. Remember zinc rich oil for solid lifters (Rotella, Amsoil etc.)

- Marshall

miike
02-01-2013, 05:34 PM
I wish I didnt need to change the helm. I am tall and have long arms and I don't want the helm any closer to me. Is the Imco helm any shorter? Will adding on the steering make me have less travel left to right or up down?

Engine is 296 duration, 600 lift comp cam with a custom grind, full roller, j&e pistons, high rise edelbrock, 9.5:1. cast iron heads, stock forged rods and crank. new bearings and rings and stuff.

I don't know much about cams and compression and how to calculate hp. Just going off what they told me.

Pat McPherson
02-01-2013, 06:37 PM
I can't wait to get my new to me 22C out on the water so I have more to contribute. My 22C with 502 mag doesn't have external steering yet and my plan is to use the existing cable helm and a "add-on" system. Don't know if you can go that route with a Cobra drive. I believe installing a cradle/race engine mount should be on your list. I've broken 2 boats before installing a better engine mount and did not have issues after. If your going to run a solid lifter cam engine with lots of overlap, you need long risers on your exhaust system. good luck, can't wait to hear how she runs.

Carl C
02-01-2013, 06:42 PM
Helms come in different sizes and I think there is a 3" one. The Bravo retains full range of movement.

miike
02-01-2013, 07:37 PM
Ok perfect, the one I have now has to be at least 3"

Thanks for all the help everyone!!

Not sure about reinforcing stringers right now. Sounds like an awesome idea, but I'm having a friend help me drop in and it's time sensitive. My buddy is a mechanic at a shop (where I used to work as a much less skilled mechanic) and he has a pretty good side business out of his house. Whenever he drops a new engine in, his other buddy comes over with a tractor and they swap out. I'd rather not have a lot of down time while I glass and redrill holes for the motor to go in. I'm pretty sure the 502 is bolt up to the mounts in on the 454, so I wouldn't have to start from scratch on the adjustment. Just drop in, line up the drive and I'll take the boat home and do the rest.

I know a lot of Donzi stringer grids have cracks at the joints and mine has a bit, but I filled them in after I bought the boat 3 years ago with epoxy or marine tex or something and they haven't reopened. Ideally I would like to beef up everything but just to get me out there again I think I will skip it this year. The 454 weighed as much or more stock than I will be putting in (given some aluminum parts now). I can take it easy and slow over the rough stuff and that's where I take the hard hits. It is very infrequent (maybe once a year I come down wrong). I'm going to let it fly this year and if things get ugly I'll get back to that. I just want to get the motor running and dialed in.

For exhaust I have stock 496 manifolds that I bought as take offs. I put two seasons on them, maybe 100hrs. I am a little worried about the reversion and have been reading the thread on that. I am planning on silent choice.

In more detail my cam specs are
296 duration, 598 lift, 108, 106 centerline

the roller rockers add another .002 lift. They are 1.72 and stock is 1.70.

Also, 219 intake and 188 exhaust valves, I think those are the sizes of the valve right?

Does anyone know what all that means? I've been looking at cam calculator websites and can't figure it out.

gcarter
02-01-2013, 07:38 PM
This is a picture of a Latham 3" helm. They are sometimes available on eBay, which is where I bought this one.

http://www.donzi.net/forums/attachment.php?attachmentid=70543&d=1332686419

Ghost
02-01-2013, 08:00 PM
Exhaust is another question with an agressive cam like you need for that sort of HP. EDIT: sounds like you are aware of reversion issues.

The beefing up of the stringers and such is not about weight, it's about the torque the motor exerts, as well as added loads on the running surface from the speeds you get with that sort of power.

Carl C
02-02-2013, 08:48 AM
I am not a marine engine specialist! I'm just posting this for comparison. The Merc HP525 EFI cam specs are:
525 EFI Cam Spec's

236/244 @ .050" (duration, int/exh)
.610"/.632" Lift Valve (int/exh)
114 LSA

Valve size is very close to yours. I think the 114* LSA is what is important to address reversion. Yours IS a marine cam right?

You will not make 600 hp with out long tube headers on a high output n/a big block Chevy.

Others here can tell you so much more....

Dr. Dan
02-02-2013, 10:48 AM
:spongebob: Eddie - (Undertaker) was pretty accurate in his summary...impressive Ed, you actually do listen to me?

Couple of my observations....and little known facts....
1.) The efficiency of the King Cobra is beeter than most people realize, the lower is actually about an 1 " 1/2" shorter than a standard Bravo set....translate into it has a built in Shorty effectively.

2.) The King Cobra although larger, bulkier, stronger, and reliable...is not the Anvil dragging the boat to a slower operating speed that people think....fact is the laminar flow of the water and the stability of the design in the drive make it so predictable that Undertaker is right I never use my tabs, they stay parrellel to the running surface...98% of my run time. Also the drive is not slow or heavy.... the polymers that compose the structure are light and strong. The water flows very well by the cone...its always surprising to watch the reaction of others I run with ...whatever they are driving.

3.) When I did my first version of the "Bull Hamstah" repower - I picked up about 20 mph(454 -330 to the HP500) ...the boat handled much better at higher speeds....in terms of a need for tabs or any derivative. The largest control factor imo is to determine the Nuetral Trim position on your hull...I wont go into the weeds on this ...but setting the drive to Nuetral will fly your hull level as a jet when running full tilt boogey. Where most....drivers of any boat get their butts in trouble is by running at high speed with the drive too trimmed in the positive direction....the hull will sky and slam and likely make for some intersting stains in the underwear of most passengers.....jus sayn?

4.) I do run 3 blades currently and the acceleration is stupid...quick, next to no slip...with a 26 TXP Turbo prop... - I want to try a Hydro 4 blade this season...likely a 25 or 24 pitch.

5.) Poodles Steering Bracket was made from the nice folks at Marine Machine...no longer in business under that name, perhaps someone is still available that has the pattern to cut the plate to do the Steering Bracket...they ran a standard cobra and a King version...fyi. One could be fabricated simple enough .... or we could run patterns off of mine...to duplicate if need be.

Feel free to call or email me if you want specifics on anything....I use my stock single ram bennetts...by the way the current version of the Hamstah is dynoed at 620 ft -lbs of Torque and had its Fuel Curve remapped and Tune done by Saris Racing /Performance Marine in Lake George... driving the boat is exciting and always lifts my mood.....for a 1993 - the 22 is the most satisfying experience I have while wearing clothes.:wavey:

Doc of the Bay :beer:

miike
02-02-2013, 12:43 PM
Ya it had truck headers on it when I got it and I told the guy I didn't want them. Exhaust might be limiting my power and I think my carb might too, because its a 750 Edelbrock, but I'm not going to worry about that the first year. Changing exhaust and carb is easy (unless needs custom headers) stuff to do and it's a lot of added expense. I'll probably be happy with what I get out of this right now, as long as I don't pull water back in.

I think this is the cam

http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=599&sb=2


but it had some of the lift taken off of it. Hopefully that is good for making it suck back in.

Any consensus on whether or not I should run silent choice. I do want it unless I can't ever use it. Don't have it now. Again these are stock Merc 496 mainfolds. Cam is like in the link above except .600 lift.

Thank you everyone!

PS- Still trying to get in touch with madpoodle for a king cobra steering bracket. Can anyone help me out with the name of other donzi board he watches?

gcarter
02-02-2013, 01:02 PM
Miike, I think you'll find a 750 is too small for that engine.
Buizilla is the carb expert, maybe he'll chime in.

Carl C
02-02-2013, 01:07 PM
I don't think you can use that cam. Where are the engine experts?

BUIZILLA
02-02-2013, 03:27 PM
BIG NO GO ON THAT CAM..... :eek: :embarasse

miike
02-02-2013, 06:18 PM
What cam should I put in? I can swap it easy until I put it in the boat.

Guy I bought engine from said the motor came with the marine 750 edelbrock on it when it was in a Cigarette, and it was jetted up. He said I could use it but that the motor could take up to a 1350 carb. He offered the motor with a 1050 on it, but I took the edelbrock because it was marine.

Carl C
02-03-2013, 08:41 AM
You need to swap the cam. You need to make sure that the entire valve train is up to running 4,000+ RPMs for long periods. You need high quality valves. You should have forged pistons and crank. Aluminum heads would be better. Long tube headers are a must for 600 hp range. You need the bigger carburetor. I'm not a marine engine builder. I'm trying to help with my limited knowledge on this. Are your starter and alternator marine parts? With the package you've described and with a cam swap you can forget about 600 hp and high rpms. I'd guess 450 hp max. If no one can help you here then there are lots of engine builders on offshore only.

Brian41
02-03-2013, 09:54 AM
Lets start with whats wrong.... cam, crab, exhaust and maybe engine internals and or clearances. Things that should be addressed on boat.... steering, stringers/engine bay, drive location and engine mounts.

To make 600 Hp out of your 502 you will need a cam with lift in the .640 range, duration in the 245 range with a LSA of 114 if you are going to run water at the end of your exhaust. Also ditch the solid cam and go hydraulic roller. RPM will be at about 5800 and switchable exhaust is out of the question. Compression would need to be 9.5 or higher making aluminum heads a better choose. Carb would be in the 950 CFM range and good flowing header style exhaust a must.

With 30+ years make boats go faster and my experience with the 22 Classics over the past 5 years I have become a bit of a master on these boats. I have 2 of the fastest 22's here now with up to 5 of them here at any given time during the season.

Feel free to contact me about your build 734-586-0448
Regards Brian

Brian41
02-03-2013, 09:57 AM
Forgot.....I even know Carl

harbormaster
02-03-2013, 11:00 AM
ok. you need cast iron heads for a more complete burn. aluminum disapates too much heat. you need inkinal valves and rectangular port heads. a dart intake is great. A high rpm 502 is a recipe for disaster. dump the solid lifters and go with a a good roller cam and roller rockers. I cannot see how you got a great motor for 4k. Just the good parts cost lots more than that. If you want call me anytime on my cell 713 898 0605 and and I can answer most of your questions. we do nothing but big blocks at Victory Marine. I will be more than happy to help you with info. I am also a Dart and Comp cams distributor.

miike
02-03-2013, 12:38 PM
You need to swap the cam. You need to make sure that the entire valve train is up to running 4,000+ RPMs for long periods. You need high quality valves. You should have forged pistons and crank. Aluminum heads would be better. Long tube headers are a must for 600 hp range. You need the bigger carburetor. I'm not a marine engine builder. I'm trying to help with my limited knowledge on this. Are your starter and alternator marine parts? With the package you've described and with a cam swap you can forget about 600 hp and high rpms. I'd guess 450 hp max. If no one can help you here then there are lots of engine builders on offshore only.

I've been iffy about the carb. The valvetrain is built. It has Comp solid lifters, Delta hardened pushrods, and stainless steel full roller rockers that are way tougher than stock. This motor is built for 7000rpm. It has forged crank, rods, J&E pistons, and perfect circle chrome rings. I don't need the 600hp so if I lose it going to the right cam, that is regrettable but that will have to be the way it is. I'll put this motor in and get it running with what I have as long as I don't need to pull it later for any reason. Doing the cam is cheap anyways, I'll change that now. Looks like I can get a marine comp cam for $150. I am using the same marine stater, bellhousing, alternator, circ pump off my 454. I was going to add FWC. I understand I need an electric fuel pump. I got an HEI distributor, I think it's the one that came with it.

I'm not going to get into headers this year. My season is short and I'd just like to get up an running without missing any good days. My manifolds are a big increase over what I was running before and if they cost me some power right now its not the end of the world.

I do have cast iron heads and an edelbrock victor jr intake. The guy had way more money into this motor than he got out of it. Even if I need to change a $150 cam I still got a steal of a deal. I'm willing to change it to make it right, but only stuff that I can't fix once its in the boat. If I come across a good carb deal I might go for it. Couldn't find a marine 850 edelbrock carb on summit or cp perf. Do they make one? Do I eventually need to go higher than that anyways?

With getting the motor in and installing the steering I'll be plenty busy. I also need to fix my stupid loose hatch because its chipping away at the rest of the boat, so I've got gelcoat work to do as well.


Thanks for all the help guys, this is really going to make a difference in how easy this project goes together!!

Ghost
02-03-2013, 01:02 PM
RE: "Couldn't find a marine 850 edelbrock carb on summit or cp perf. Do they make one? Do I eventually need to go higher than that anyways?"

What HP are you targeting?

Brian41
02-03-2013, 01:10 PM
If you insist on using the items you already have then your HP target should not exceed 450. The 750 CFM carb you have now is plenty. Do yourself a favor and change to a hydraulic cam and order lifters with it.

miike
02-03-2013, 01:20 PM
Ahh one more thing,

Not sure if the oil pan will clear or if I have to buy another. And then, the oil filter is down low on the block. Is there a remote oil filter kit? My 454 had it mounted to the riser before I ditched the stock manifolds. Now the oil filter is still a remote housing but floating above the manifold.

edit and another thing,

So if I need to change the cam, why not keep the solid lifters? They have the poly lock things on them and I don't mind doing a valve adjustment every 100-200 hrs.

JayZ
02-03-2013, 03:23 PM
You should be able reuse your remote oil filter. I did on my '93 King Cobra boat.

You might have to get a new bracket or make one.

BUIZILLA
02-03-2013, 04:38 PM
you'll make more power with a solid roller, but not at the rpm level you need to run..

get a hyd roller cam and hyd roller lifters, and sell whacha got..

750 is a marginal, but usable, choice.. provided it's a double pump mech sec version, it's not a marine carb but i'm very fond of the HP950 that Holley puts out, really crisp carb

Comp offers a generic hyd roller is the mid 270ish duration range on a 114* LS, go with that, or maybe something in the low 280ish range..

Carl C
02-04-2013, 08:48 AM
I'm a little confused here. It sounds like you bought a hot rod truck or car engine. You said that it had truck headers and that is a drag racing cam that makes peak hp at 7,000 RPM. I have 20 years experience working as a heavy repair auto technician. I have never built a marine engine but have learned quite a bit about them. I am not going to try to tell you what parts to use but I do see some glaring issues. Are the heads aftermarket or stock? You need to make sure that it has marine quality valves (inconnel?). Stock valves will not take the abuse that a marine engine sees. You say it is 600 hp but that is at 7,000 RPM and for a few seconds at a time. You need to put your peak power closer to 5,500 RPM. You need lots of low end torque or you won't even get on plane. You need a 114 LSA marine cam. You need long tube headers. I wouldn't buy used ones since they have a limited life span. You need to be sure that the starter, alternator and distributor are marine parts. Hopefully you have a stout and properly assembled short block. Do all of that and you should have a nice package. With 9.5 compression you might be looking at 89 octane fuel or more. Forget the k-planes. You have some engine parts to buy. Brian and others on here are qualified to advise you on a proper combination of parts. Good luck. It sounds like you have a good engine to start with. The HP525 EFI is a 502 BBC built by Mercury Racing BTW.

VetteLT193
02-04-2013, 11:14 AM
:spongebob: Eddie - (Undertaker) was pretty accurate in his summary...impressive Ed, you actually do listen to me?

Couple of my observations....and little known facts....
1.) The efficiency of the King Cobra is beeter than most people realize, the lower is actually about an 1 " 1/2" shorter than a standard Bravo set....translate into it has a built in Shorty effectively.

...

This is the first I have heard this. I did a LOT of research on the OMC vs Merc drives back when I was looking for my first Donzi. The OMC boats could be bought for far less $$ so it was certainly a consideration. Everything I read said the cutouts are the same and the distance between the input/crank shaft and the prop shaft are the same. That's a major difference!

miike
02-04-2013, 01:40 PM
Its peak power is 5500 rpm, but I'm not going to prop it like that because I want a slower cruise. I have all the marine starter etc, and the motor was set up to go in a truck but the guy changed his mind. It originally came out of a cigarette, I'm not sure if they meant a Cigarette brand boat or cigarette type boat. Either way, it had a marine carb, distrib., and valves. I will repaint all my grey OMC stuff, power steering, alt, water pump to put on it because I didn't get any of that with it. I have to reuse my flywheel, bellhousing, starter.

Looks like right now I need to change the cam because this 108-106 centerline business is going to cause problems. The Merc 496 manifolds are as nice a set as any without going to headers so I'm going to keep them. I'm not going to spend the money on the silent choice because people are saying that it's a no-go over 500hp. I looked at the 1050 Holleys and Quickfuels and that appears to be a major pain in the ass. I don't want to have to deal with setting up the carb and all that stuff while I'm trying to break in the cam. I'm just going to throw the 750 Edelbrock on it, it's dialed in for that motor already. I don't need all the speed and hp my first season out w/ this motor. I'm ok with building up to it and getting the seat time as I learn the speeds anyways.

miike
02-04-2013, 01:53 PM
you'll make more power with a solid roller, but not at the rpm level you need to run..

get a hyd roller cam and hyd roller lifters, and sell whacha got..

750 is a marginal, but usable, choice.. provided it's a double pump mech sec version, it's not a marine carb but i'm very fond of the HP950 that Holley puts out, really crisp carb

Comp offers a generic hyd roller is the mid 270ish duration range on a 114* LS, go with that, or maybe something in the low 280ish range..

If it's not important to run a marine carb, then I can get the 850 double pumper the motor was offered with.

As far as I know, the only difference in a marine carb is that one of the linkages is sealed to prevent fuel from dripping out. Should I stick with marine 750 or go to non-marine 850?

BUIZILLA
02-04-2013, 02:25 PM
the marine carb will have teflon seals on the throttle shafts, and rollover vent tubes

i've personally never seen backfire flames come out of the throttle shafts but thats what the teflon seals there are for, and if fuel puddles on top of the throttle blade it can't work it's way outside the carb base..... if you run a spark arrestor or air cleaner the vent tubes are still inside that area anyway, so I wouldn't sweat that detail..

JayZ
02-04-2013, 03:19 PM
Its peak power is 5500 rpm, but I'm not going to prop it like that because I want a slower cruise. I have all the marine starter etc, and the motor was set up to go in a truck but the guy changed his mind. It originally came out of a cigarette, I'm not sure if they meant a Cigarette brand boat or cigarette type boat. Either way, it had a marine carb, distrib., and valves. I will repaint all my grey OMC stuff, power steering, alt, water pump to put on it because I didn't get any of that with it. I have to reuse my flywheel, bellhousing, starter.

Looks like right now I need to change the cam because this 108-106 centerline business is going to cause problems. The Merc 496 manifolds are as nice a set as any without going to headers so I'm going to keep them. I'm not going to spend the money on the silent choice because people are saying that it's a no-go over 500hp. I looked at the 1050 Holleys and Quickfuels and that appears to be a major pain in the ass. I don't want to have to deal with setting up the carb and all that stuff while I'm trying to break in the cam. I'm just going to throw the 750 Edelbrock on it, it's dialed in for that motor already. I don't need all the speed and hp my first season out w/ this motor. I'm ok with building up to it and getting the seat time as I learn the speeds anyways.

.....Mike, You've got a LOT going on here.

Let me start by saying that I am far from an expert but I have a similar boat to yours and have already climbed my way down the decision tree that you are faced with. I'll try to share some of my thoughts here.

First thing as you know is make sure this thing is set up to run in a boat. You're working on the cams, let's hope that the valves are inconel. I'll assume you know this but just in case, make sure you have the right freeze plugs made of brass for marine engines.

As I understand it the big problem with a cam with alot of overlap is the reversion issues the other is you need to make power at the right RPM band.
...I think you could run a dry exhaust to avoid the reversion issues if you wanted to but that wouldn't be my choice.

Your choice of exhaust (496)is exactly what I am using on my 502 that I'm stuffing into my King Cobra boat. Make sure you have the short risers because the tall ones won't fit.

You can relocate your remote oil filter from your OMC boat but you'll either have to hang it on the transom, stringer, behind the seat or find or make a bracket to mount to the 496 manifold. Mine is a fabricated piece and I mounted it on the 496 manifold.

While we are on the subject of oil, you will probably have to get a new oil cooler for your high H.P. boat rather than the small one that came with the OMC motor. ...assuming yours is the same as my set up.

I think the high H.P. oil coolers call for a 1 1/4" raw water hose. The OMC boats have a 1" feed coming off the transom plate so you'll have to address that somehow.

-not sure what you are doing with regard to the obsolete water pump or the spitfire igntion stuff along with the shift assist but hopefully you've already gone down that road. If you put this High H.P. big cam motor in your boat it won't idle down at 850 RPM so shifting without a shift assist might be a bitch.

As for the silent choice, the geometry for you boat (OMC/ 502/496 frankenboat) is going be anything but stock so be careful in choosing your diverters so that the fit your set up. You mentioned silent exhaust are no good at 500HP but I'm pretty sure there are some folks here that use them in their High H.P. boat (Carl).

Here's a pic of my 502 with the 496 exhaust and the OMC remote oil filter. ...need to paint it still.

Good Luck with your project.74507

Pat McPherson
02-04-2013, 08:57 PM
The 750 carb you have is good on a stock 502; merc used them on both the 454 and 502mags in the early/mid 90s. I've got one on my stock 502mag. A 750cfm will flow enough to about 5000rpm on a mild 502 up to about 450HP.
The cam you have needs to be changed. I suggest buying a used 502mag or 500efi roller cam; they can be had from guys doing upgrades for $100. Then buy new hydraulic roller lifters to match. Any bigger cam than the 500efi with the exhaust you have is a receipt for reversion.

yeller
02-05-2013, 05:06 PM
The Merc 496 manifolds are as nice a set as any without going to headers so I'm going to keep them. I'm not going to spend the money on the silent choice because people are saying that it's a no-go over 500hp.If you can afford it, I personally recommend the silent choice. Too many people ditch them as well as mufflers because they want "the sound", yet complain when speed laws are implimented. If boats weren't so damn loud, there wouldn't be nearly as many complaints about them. You're rarely going to be running your boat in the 500+ range, so you'll have them "open" at that point.
I have over 500hp on the engine I'm putting in my boat and will be using the silent choice...and mufflers. I love the sound of the boat through the stock Corsa mufflers and wouldn't want it any louder. The silent choice is awesome when doing a slow cruise and trying to hold a conversation......plus when you quietly pull up to the dock, people want to look at your boat instead of complain about it.

Just my 2 cents.
Putting away soapbox......:)

JayZ
02-05-2013, 06:56 PM
Mike,


For some reason my previous post didn't take so I'll try again. Sorry if it gets duplicated.


You've got alot going on here.

I'm by far no expert but I have a similar boat and have gone through the same decision tree your going through.

First, make sure you truly have a marine engine. Cams -Your working on. Valves??? inconel and don't forget freeze plugs need to be marine plugs made of brass. I think that there are other things like tolerances when assembling etc. but I'll leave that to the experts.

As for your cam you know you need to avoid reversion issues or go with a dry exhaust (wouldn't be my choice) and you have to make power in the right RPM range.

One other thing if you have a lumpy cam you won't be able to idle the boat down low at 850 RPM so you need to make certain you have a shift interrupt that works. Hopefully you've already thought through all of this and maybe even have it figured out. I've been told that you can still shift these KC drives withouth the interrupt if you have a very low RPM setting at idle but I cannot speak from experience.

As for exhaust, I used the same 496 exhaust on my King Cobra project with 502 and it works but you need to make sure you have the short risers because the tall ones won't fit.

You will also have to fabricate a way to mount your shift bracket and your Remote Oil Cooler off your OMC boat. I can send you pics of what I did if you like although I'm thinking of mounting my shift bracket on the transom if I can find a clean way to do it.

For the silent choice like Yeller mentioned you can use it in High H.P. motors. Carl has it on his 525. You have to remember that you are going to have some weird geometry going on with the 496 Mercruiser exhaust on an OMC boat with a 502 in it so I don't think it will be a simple plug and play anway.

Good Luck and post pics.

Jay

miike
02-05-2013, 07:34 PM
Ya I totally agree. I put thru hull exhaust on my boat the first year I got it and last year I was thinking, man I want silent choice next year. I would do it, and it's totally easy to do because my y-pipe is still down in the boat with block offs in it, and there are used silent choice diverters all over the internet, but everyone is telling me to forget it.

Right now, I'm considering full dry exhaust risers because it might be easier to do that than go in and swap my cam and springs and lifters. Unfortunately that noise would be horrific and there's no spot for a silent choice.

People are telling me, as you can read above, that my cam is totally wrong and is going to cause trouble. It's not that I don't believe them, because I don't know squat about cams, but I remember when I started out as a boat mechanic at Olympic Boat Centers, they had 28 Bayliner Discoverys that would suck water into stock 350s with Alpha drives. The same motor in the same boat with a full inboard shaft wouldn't do it.

I'd like to not have to mess with my engine because its got a lot of custom valve work done to it, but it might have to be redone.

Pat McPherson
02-05-2013, 08:36 PM
Right now, I'm considering full dry exhaust risers because it might be easier to do that than go in and swap my cam and springs and lifters.

I thought you have a set of 496 manifolds and risers?
I've got a ZZ502 roller cam you can have for the cost of a 30 pack of Bud Light. The cam is very close to the cran cam used in the Merc HP500 carb engines. The GM Springs and Lifters are not that expensive.
If I'm reading all the opionions and your messages correctly, you don't want that big solid lifter cam and the need for dry exhaust...

miike
02-05-2013, 10:28 PM
Hey thanks a lot, where are you located?

Mike

BUIZILLA
02-06-2013, 08:23 AM
the ZZ502/502 cam, part # 12356543, most commonly found in ZZ502 crate engines, is NOT for marine engines

it clearly states that in the GMPP catalog and literature

I had a 454/425 HO GM crate engine in my Criterion for the last 9+ years.... hyd roller cam #24502611, this is a 112* LSA which worked okay, because it had 19* spread on the valve openings, which really helped soften the reversion pulses...the 502/450 HO crate engine used this same camshaft... obviously, I had ZERO problems with it...

as with any steel billet roller cam you must run a melonized distributor gear #10456413

just an FYI

roadtrip se
02-06-2013, 03:22 PM
Ok perfect, the one I have now has to be at least 3"

Thanks for all the help everyone!!

Not sure about reinforcing stringers right now. Sounds like an awesome idea, but I'm having a friend help me drop in and it's time sensitive. My buddy is a mechanic at a shop (where I used to work as a much less skilled mechanic) and he has a pretty good side business out of his house. Whenever he drops a new engine in, his other buddy comes over with a tractor and they swap out. I'd rather not have a lot of down time while I glass and redrill holes for the motor to go in. I'm pretty sure the 502 is bolt up to the mounts in on the 454, so I wouldn't have to start from scratch on the adjustment. Just drop in, line up the drive and I'll take the boat home and do the rest.

I know a lot of Donzi stringer grids have cracks at the joints and mine has a bit, but I filled them in after I bought the boat 3 years ago with epoxy or marine tex or something and they haven't reopened. Ideally I would like to beef up everything but just to get me out there again I think I will skip it this year. The 454 weighed as much or more stock than I will be putting in (given some aluminum parts now). I can take it easy and slow over the rough stuff and that's where I take the hard hits. It is very infrequent (maybe once a year I come down wrong). I'm going to let it fly this year and if things get ugly I'll get back to that. I just want to get the motor running and dialed in.

For exhaust I have stock 496 manifolds that I bought as take offs. I put two seasons on them, maybe 100hrs. I am a little worried about the reversion and have been reading the thread on that. I am planning on silent choice.

In more detail my cam specs are
296 duration, 598 lift, 108, 106 centerline

the roller rockers add another .002 lift. They are 1.72 and stock is 1.70.

Also, 219 intake and 188 exhaust valves, I think those are the sizes of the valve right?

Does anyone know what all that means? I've been looking at cam calculator websites and can't figure it out.


I just stumbled on this, as I have been focused on winter sports, and not the Donzi.

Besides all of the engine set-up feedback you are getting, I would heavily reconsider the set-up of the boat for the power.
FWIW, my stingers and bottom had issues with the stock 470HP 500 EFI, and it wasn't the hits that did it, it was the torque
of the engine twisting the boat. I am running a little more than that, but not until after significant upgrades to the boat.

There is a wealth of knowledge out here on how to make these boats live under high horsepower conditions. I would suggest
doing a search and taking a look at the experiences of others that have already gone down the route you are going. This is
what makes theis community great. Get in a hurry, and slam that engine in there in an afternoon, and if that engine makes
any power at all, your boat is going to start coming apart in quick fashion. These hulls werene't designed for this sort of power.
Slow down and do it right, as there is plenty of knowledge here to help you along the way. Have fun at it, but taking short cuts
will cost you more aggravation in the long run.

Pat McPherson
02-06-2013, 08:02 PM
the ZZ502/502 cam, part # 12356543, most commonly found in ZZ502 crate engines, is NOT for marine engines

it clearly states that in the GMPP catalog and literature

I had a 454/425 HO GM crate engine in my Criterion for the last 9+ years.... hyd roller cam #24502611, this is a 112* LSA which worked okay, because it had 19* spread on the valve openings, which really helped soften the reversion pulses...the 502/450 HO crate engine used this same camshaft... obviously, I had ZERO problems with it...

as with any steel billet roller cam you must run a melonized distributor gear #10456413

just an FYI

The zz502 cam has nearly the same specs as the crane cam used on the Merc HP500 carb engines; something like 224 intake, 234 exhaust 110 LSA. It will work on a marine carb engine, just not with efi. Probably not a good cam to use if you want captain's call, but neither is the merc/crane HP500 cam.
I have also used the 454/502 HO cam in a marine engine and it runs about the same as the marine mag cam on a carb engine. I've got one of those on a shelf somewhere too. Like the zz502 cam, the HO cam does not work with efi; not enough vacuum at low rpm. I'd say this one would be fine with captain's call.
These GM cams cost a fraction of the crane cams merc uses.
I'm in CT.

BUIZILLA
02-06-2013, 08:44 PM
there are 2 GM cams shown that match kinda closely to the HP500 spec's BUT they are out on 114 and 115 LSA's..... where they should be

i've only built usable engines making up to 2.8 hp/ci so i'm not sure why you think that low vacuum is a detriment in a pressurized rail, port injected, efi world.... the 110 will make less vacuum than a 114 will and have a choppier idle.. it doesn't say anywhere in the GMPP catalog not to use either the ZZ or HO cams for EFI, it does clearly show that the ZZ502 cam is the only one NOT to be used for marine use

don't shoot the messenger, argue your case with GM

at this point, i'll step aside with this topic :lookaroun:

harbormaster
02-21-2013, 05:11 PM
Hi Mike,
I looked overyour configuration,

Your comp cam,(296 duration, .598 lift, 108, 106 center line) is too big. The solid lifters are also a no go.
My recommendation is a HP500 Cam and hydraulic roller lifters. I can provide these for$700.

Your 219 intake valves are also too small. I would recommend 2.250 intake valves.

The Victor Junior is too small. I recommend a Dart intake with large runners. $300

The carb is way too small unless you pay a lot to have it reworked. I recommend an 850 Holley with a 4 corner idle circuit.

As for exhausts, the CP Performance/Hardin Marine manifolds (Gil Lookalike) would work well. I recommend these because we have had problems with the EMI Thunder, and Stainless Steel Marine getting water into the engine because of the porosity of the aluminum, and also condensation.

The way your engine is currently configured it would lean out at higher RPMS and most likely fry the engine.
With the changes I recommend you will have a really dependable solid 500HP engine.
Scot

gcarter
02-21-2013, 06:45 PM
It won't cost a single penny to take heed concerning what Todd (Roadtrip) said in post #53.
Since you have a KC drive, I'd also assume the boat is pre '94.
Take a few minutes also and read a dozen or so pages of this thread;
http://www.donzi.net/forums/showthread.php?50476-Now-I-m-getting-serious/page4

There's a lot more to building a fast boat than bolting in a 500-700 HP engine.
What you'll see in this thread is a lot of damage caused by high HP w/o reinforcing the hull.
The boat may not sink under you, but it will be literally beat to pieces.