Marine 318's

I just got back from Florida, and my father has a spare 318 out of his shrimp boat. what are the differences in these vs. the car/truck engines? he seems to think they got steel cranks, heavy duty rods, select blocks etc, but he really isn't sure, and ive never been into boats(my favorite ones are the ones that don't sink!). anybody know?

I would imagine they are similar to the 273 marine engine. I have a 4 barrel intake for a 273 marine. Intake is a little different than the street manifold.

More nickle content (to avoid rust)in the block.
Cam and heads suck for street. Watch for left hand rotation motors too.My son's Conqueror 318 jet, needs a marine cam.
My 88 Ramcharger engine is in it and it doesn't like the cam.

Might be a brass or plastic impeller water pump, but no biggy.

Some were reverse rotation. I had a 340 out of a boat and it had a VIN for a 70 Swinger on it, so it had been replaced at some point.

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Might be a brass or plastic impeller water pump, but no biggy.

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If it's straight inboard. then neither brass nor plastic.

Raw water system has 1 pump that uses a separate, or external, pump that pumped water thru the motor. The standard pump is eliminated. This is the most common system.

Closed system uses 2 pumps, a standard automotive pump that pumps water to a cooler which which is cooled by a raw water pump. This system keeps salt water out of the motor and allows for antifreeze just like automotive, no need for special impellers.

I/O I don't know about.