Is a 350 Chevy Mercury Marine motor & a 350 Chevy Car motor interchangeable? What are the differences?

Answer 1

The answer your looking for is they are not compatible.
The differance in a marine engine is in a marine engine is they use brass freeze plugs instead of steel which will rust out , the camshaft is differant because marine engines run in a differant rpm range than a automotive engine and also the valve springs are heavier due to the type of camshaft.And in most marine applications the oil pans are differant
Nowadays they do not manufacture reverse rotation engines the only ones available are remanufactured aftermarket one for the older engines.
The newer engines all use standard rotation and reverse it using either in board transmissions where they can reverse operation by turning pump in opposite direction or counter rotating sterndrives.
My knowledge comes from being a Merury certified tech for 19 years .Hope this helps

Answer 2

No, Many marine engines are set up to run backwards. They also are made for low end torque and not higher Rpms like car motors. Camshafts are different. This is Not a good swap.

Answer 3

There would be too many changes. That engine is built for a different purpose than an auto. Consider getting a short block if you need another engine or just get a crate engine.