TomZ

OK, I'm about tired of this particular setup that my builder cannot get right. I have an engine that is perfectly suited for drag racing, but completely useless for the marine environment. My biggest problem is that it has too mcuh cylinder pressure. I'm pushing 200 PSI after four revolutions of the engine during a compression test. I spoke with Dennis Moore and he suggested retarding the cam timing to a 110* intake centerline to reduce the cylinder pressure some, though I've found that I'd have to really retard (in other words, get a completely different cam) in order to make any real difference (I could probably get it as low as 190 PSI by retarding). So what I have now is a high compression small block that I cannot run hard at all due to detonation. I explained this to the builder, but he built it this way regardless of what I said. Unless there is some really good advice on how to get this to live in the boat, then I'll be tearing it apart over the winter and doing it right (which I should have dome originally anyway).

How should I do this thing up? I still going to run the Vortec heads, but what about cam and compression? I might even go roller to get the power up. I want to do this right and I'll be doig it all myself.

This thing has been beyond frustrating. Any suggestions would be great.

Thanks!

audacity

drop a stock 500 hp in and call it good

audacity

you never said what boat hull it's in... or what other componets are in the boat??

TomZ

Booat specs:

'83 4 Winns 225 sport boat, low drive height, etc. 20-something degree deadrise.

3498 pounds unloaded. Hold 70 gallons of fuel, etc. Estimated weight is roughly 4800 pounds with the wife and I with fuel, etc.

This all started because I could not get the boat to run well with the props that I had. Speed was just about the same with as with my old crappy motor. I could not turn the right RPM with a 17 or a 21 (though all the calculators said that a 21 or 23 would do it right) and then the engine melted an intake valve (which I was told was because the valve was defective... BS I think). So I took it all apart, put in new Ferrea valves, and ran a new compression test. Pressure was at 200 PSI on all holes. I can't use the engine this way.

So now I'm here.... frustrated.

audacity

put it back to stock and have fun....sounds like you have and will continue to open can after can of worms...what about the drive...alpha, yes? or omc...not the king cobra...external steering?? x dem. you said was low...

cobra marty

There are some nice stock crate engines out there or rebuilds. Save yourself the headache. Try 1-800-runs-new, and others.

TomZ

I'm not one to give up on these things and I don't think that I'm going to open up another can of worms with it. I'm not asking to be flying down the river at 80 MPH, I just want it to run better. I don't want it to be a go-fast boat. My goal was to make it perform better. It will perform better, the problem is that the engine is not usable in its current form because of the compression.

I have an Alpha on the boat. It will work just fine if I baby it out of the hole (the boat goes absolutely berserk out of the hole if I gag it hard anyway... I don't like that) and just be nice to it.

I was just talking with the builder (I don't know why I even bothered) and he said that I could easily knock off about 15 PSI by retarding the cam by 8*. Maybe I'll try that first.

audacity

Tom,
good luck brother...A LOT of people out, some here on this board, have made the mistake too...the marine environment is VERY unforgiving unlike passenger vehicles. the engine is one of LAST areas where you should look for performance gains and the most unreliable...HELL, even my friends do it after i drill it in 'em...take a damn good running boat with an engine that will go over 400 hours in stock form...mess with it, go slower, blow drives, puke engine in under 50 hours...miss a ton of great weekends,,,,on and on and on,,,for what 2 mph???...DON'T look at a boat as seperate systems,,,,look at it as one and address them in a logical order....my opinions are based on; i like to boat EVERY weekend, i like to win races and you can't do it if you don't start or finish.

tom, don't take this the wrong way....i love the water,,,no matter if it's in our low budget bayliner, racing the APBA pro series, on our poker run boat, or racing sail boats....cobra marty and i both are just look'n out for ya....we see a lot of sob stories here


ps...one you may not thought of...take a 10 year old drive that has run within X parameters....now increase loads and rpms.....good luck! it's not a good thing to ask ANYTHING to do something it hasn't in 10 years.

traviss

I am running the vortec heads, RPM air gap intake, 750 holley, EMI exhaust, crane roller cam, 222-230 dur, .509/.528 (.543/.563 lift with 1.6 rockers on mine) with SRP dished piston to match the combustion chamber w/ comp ratio of 9.9 to 1. ( compression test .. all cylinders were around 185 PSI). total timing at 32. spins my 25" at 5300. perfect. i guess around 400-410 hp.. I have put 78 hrs on it with only one wierd piston failure.. But 58 hrs since that. and it is not babied. I run here 4000 rpm plus all the time, she has held to gether and the alpha drive is just fine too. 18.5 ft.. 2650 dry wieght. stock 270 hp mag did 58 mph, now with the 383 i saw 73.1 on gps..

This winter bigger heads and maybe a little bigger cam, and EMI's stainless tube riser's . Chatted with dennis Moore and he said if i didn't want to increase my RPM past 5300 to just put a set of the GM "fast brun alumnuim heads with there 200cc intake ports and big valves. I think i am headed towards a bigger head and increase my rpm to about 5500, and a little bigger cam to go with it.. Gotta do my homework for a few months before i find the perfect combo..

If you just want a nice motor to make boating a little more fun, don't go wild, just make a little power and get relaibility. Myself I have nothing to lose, so i go wild, if it scatters I have a spare motor for a backup..


Good luck

Travis

NASTY HABIT

TomZ might try bending this guys ear , he has built quite a few Marine 383's mine being one of them Doug 419-389-9990 prob have to leave a message but he'll call back good luck