As far as I know, marine internal combustion engine needs:

1. Ouboard water heat exchanger for engine coolant,
2. Engine sump water coil or oil heat exchanger for oil cooling,
3. Engine exhaust manifold with cooling jacket,
4. Exhaust cooling by water injection and water ingestion blockage by proper
exhaust elbow,
5. Water jacket for cooling marine gearbox and propeller shaft thrust
bearing,
6. Proper self priming outboard water pump supplying above circuits.

A propeller driven Florida Swamp Airboat is the only boat without these
items!

Regards, Tadeusz