All I have a mildly built 355 chevy that has a marine cam and aluminum heads, full roller rockers, cam, and timing set. Could this be used in a boat???? I have heard mixed opinions. this is a brand new freshly built engine all bearings are new , new pistons, edelbrock heads, comp cam's extreme marine cam. I was originally going to put this in a car but sold the car. Anyway, I found a boat I think it would be fun to put in. Just wondering if this would work? It has never been run.

Work, yes---but it will need more marinizing. For safety reasons, it will need a marine carb, marine distributor, alternator. Chances are you will need aftermarket exhuast also.

Been my experience that marine motors besides having all the safety and brass stuff need to produce a lot of torque and carry it throughout the power band.
Someone once told me a car motor in a boat and the boat would not get out of it's own way and a marine engine in a car the car would beat itself to death.
I just drive 'em (both..one sometimes better than the other)

brass freeze plugs too...

I'd anodize the aluminum heads unless they are marine heads already done. Also what's the compression ratio? They usually go lower on marine engines to reduce the chance of detonation. Exhaust valves are usually changed to Inconel, or if on a budget stainless steel.

Michael

Usually, piston to wall, ring, bearing clearances are different on a marine engine because its running sustained high RPM's

The stress on a marine engine is like driving your automobile in first gear all the time. That's why marinizers start with the heavy duty truck engine and go from there. Good things to have are 4-bolt main bearings, a forged steel crank, a cam grind that works in the RPM that benefits marine use, forged pistons, brass freeze plugs, heavy duty valve train, etc.

If you are cooling the engine with salt water, a minimum of aluminum is better. A passenger car engine will have a very short life as a marine engine.

Compression ration should be 9 to 1, The motor is a long block out of a truck 99 chevy Vortec. It is a two bolt main but has been balanced and new rod bolts etc. the aluminum heads are off the shelf Edelbrock Performer heads old style with the same size 64cc chambers that the stock vortec's have. I used stock gaskets so I'm guessing that 9 to 1 would be pretty darn close. The heads most likely do not have anodizeing they are stock , and have whatever valvetrain comes stock in them. They are good to like .550 lift. I have steel roller rockers, comp cam's marine cam with operating range of 1000 to 5000. I have no carb, ignition, or exhaust for it. I was thinking of swapping this into an application that currently has an old Merc 260 hp 350.

I'm not sure about the freeze plugs. I will have to check on that. Also Running in fresh water only.

If that's the case, then why can't they develop a transmission just like a car that can lower the stress on the engine?

Nothing will lower the stress. You could lower rpms, but that increases the strain. It's better to rev them than to lug them. Merc did make a trans to give a low gear for holeshot, not many bought it.