5.7 L mercruiser questions

[jrcengineering]

I am going to be rebuilding my 350 this winter and i have a couple questions . First off this boat is way under powered , you can really feel it drag when there 4 or more people aboard . This motor is a standed chevy 350 which i am very good at rebuilding. i want to add more power . Has anyone ever heard of using aluminum heads or an aluminum intake manifold. I will be increasing the bore and stroke of the engine but i still would like more power. I will be upgrading the camshaft as well as the lifters,push rods,rockers,and valve springs. I guess im woundering if there is any difference between boat heads and normal cast iron heads from a car .

 

[Summer Fun II]

Are you pumping it up to a 383 ??

Welcome to CSR. :smt001

 

[Kay Lee]

The main issue is with dissimilar metals. Mixing of aluminum and cast iron can increase corrosions problems, but if you flush regularly or only boat in freshwater, problems should be greatly minimized. A set of Vortec heads and a Vortec intake is a good choice however a good set of aluminum heads and intake will save you weight, too! A set of aluminum exhaust manifolds will save more weight. Build the engine for torque. Stroking is a good start. Use a 4x4, RV, or towing application cam. A dual-plane intake is best for torque. Check your ignition system for a rev limiter. You don't want to build a motor that makes it's power beyond the limit of the rev limiter.

Good luck,
Larry

 

[Lazy Daze]

I can't comment on your specific questions, but just a couple thoughts that may help save you some money...

-- That engine should do just fine with your boat... Assuming it's making good power/compression, which maybe it's not and maybe that's why you're dissappointed. Granted, it's no speed demon, but should do fine.

-- Is the engine running well? Is the boat bottom clean?

-- Are the tabs working properly?

 

[magster65]

I am going to be rebuilding my 350 this winter and i have a couple questions . First off this boat is way under powered , you can really feel it drag when there 4 or more people aboard . This motor is a standed chevy 350 which i am very good at rebuilding. i want to add more power . Has anyone ever heard of using aluminum heads or an aluminum intake manifold. I will be increasing the bore and stroke of the engine but i still would like more power. I will be upgrading the camshaft as well as the lifters,push rods,rockers,and valve springs. I guess im woundering if there is any difference between boat heads and normal cast iron heads from a car .

My experience has shown that an intake swap will save weight but won't give you any... you may even lose hp under 5000 rpm. I have an old 'Hot Rod' magazine where they test a dozen small block intakes... only a couple of them were any better than the stock intake and that was at higher rpms. Replacing the heads will give you a little extra power. Check the spec sheet for the power curve though... you don't want the high rpm units. Same goes for the camshaft, boat motors are luggers... a 'stockish' grind is best. The biggest bang for the buck might be the 400 crankshaft. The extra torque of the stroker motor will put a smile on yer' face!
:smt038
There's a few other considerations regarding that build... I found a little write-up on the 383... enjoy.

 

[Dick Whetstone]

What ever you do to the 350, make sure your drive will handle the extra power.

 

[Nassau Weekender]

Which ever motor you decide to build get it flowed and balanced. But do NOT lighted the flywheel/flex plate assembly.

Makes a nice difference to the even the stock 350

 

[Dave8792]

Please keep posting what you are doing to you motor over the winter. I'd love to see how it comes out. Are you planning on dyno'ing before and after to map what kind of differences in performance you have achieved?