It's possible boat designers built in sufficient air movement without an electric fan. The B323 has small vents high on both sides of the companionway walk-thru to vent heated air, I assume when the engine is off.
My boat has 4 clam shell vents across transom one is hooked to blower .4 X 4inch flex hoses run into engine compartment ,plus the 2 vents high on both sides of the companionway . Blower turns on when key is first turned .
I leave the key on for a few minutes after coming back into the dock to help cool compartment . This is factory.