View Full Version : Need more power
06-23-2012, 01:19 AM
Have stock 240 hp pcm 351 in powerslot. (1983 ) Need more juice for serious pulling. Marine engines are all about the torque so what is the best way to add power? Heads? Manifold? Cam? More compression? Am new to forum and marine engines so looking to gain insight from those wiser than I in this area. Got the velvet drive right thanks to some help from Kyle!
How extreme do you want to go and how much money do you want to spend?
Yank the engine and tranny as a pair over winter.
Buy gt40p heads and have the head bolt holes drilled to 1/2".
Buy an Edlebrock performer intake
Buy a different cam
Have the bottom end punched over and the crank resurfaced if needed
Should run 325hp
If you want more add a bigger cam or roller rockers.
A different prop will be needed
Estimated cost 3k to $3,500 if you turn the wrenches and well worth it. That boat will come alive hands down.
Currently your cam and heads are flat out a complete waste. If you want to save $250 then run the intake you have.
If you have any questions look at my friends under my profile and ask Phntmski what he thinks of his new engine that I built for him.
If you are looking for 400hp then the heads and cam will need to be different than suggested above. Also maybe a stroker kit and different pistons. I'm running pretty much a factory cam, and short block. Heads and intake are upgrades. One day I may consider 1.7 ratio roller rockers.
06-23-2012, 10:00 AM
Thanks Kyle. Looking to be 300 to 325 hp not extreme. Do you know what the stock compression ratio is? Can't seem to find it listed anywhere. Valve cover sticker specifies premium leaded fuel so am using additive until winter to save the valves I have. Is prop upgrade needed at 300+ HP? Is 14x18 now. Don't need to go faster, just pull harder. Thanks for the trans info.
I have 300-325 Hp.
The prop is an added extra not a necessity.
I run 87 octane and I have no issues at all.
06-23-2012, 01:16 PM
ask Phntmski what he thinks of his new engine that I built for him.
I'm running pretty much a factory cam, and short block.
Heads and intake are upgrades.
One day I may consider 1.7 ratio roller rockers.This is something that may happen on the other MC 78 S&S sitting here.
Was never much a fan of the 351 when forced to rebuild the local Police fleet in those days.
I was the 440 guy then. As simple and brutal power stock, I find it a little odd it wasn't one of the options in these boats. Must of been cheaper going Ford.
The 340 was a mean motor as well, built from the 318's. But those days are gone.
But willing to give this guy a second life one more time.
Intake is off - Pile of rust poured out of cooling ports when inverted.
So the heads better come off now - and super power flush the block.
Considered going aluminum intake - unless not suggested.
Definitely room for much improvement through out.
Ever do any oven baked Teflon coatings on engine parts?
I loved it 30 yrs ago.
I'll tour the links to see what was done - Thanks for the tips on that.
east tx skier
06-24-2012, 12:05 PM
Start with a good modern prop from Acme or OJ. Then do the heads and intake manifold. Should be close to 300 HP and, with the slot, should ne an absolute beast for under $1,000.