Re: Raw water cooling or fresh water cooling?
How long do you plan to own it?
If more than 5-7 years, the closed cooling is worth it.
But if its under a new boat warrantee, you might have to use a Merc approved kit.
I have an old boat, original engine, 26 years old, uses in salt at least half of that. Engine has not rusted through yet but if I put in a new crate engine FOR SURE it will have at least a half system on it. Not running salt water through a brand new cast iron engine.
Its worth it because:
A GM 4 cyl was designed to run at 190* not 160* that you have to use for open (raw water) cooling. Running at the proper temp reduces fuel dilution of the motor oil, and the engine will run more efficiently.
Its easier to winterize, all you have to drain is the raw water side (heat exchanger, hose from the impeller, manifold).
It will last longer, a pressurized cooling system eliminates localized hot spots in the block and head that you can have with open cooling.
Its much more work and much more expensive to replace a long block than simply replacing an exhaust manifold and riser. You're talking thousands vs hundreds and a full day of work compared to an hour or so to do a manifold.
