Behind the boat look at the prop--if it needs to turn clockwise from that position, then the engine will need to turn in a counter clockwise rotation from the front of engine view--------and that's reverse rotation

If the prop needs to turn counter clockwise from the rear view----the engine will be clockwise(standard automotive ) from the front--------

Then there is V drives?????????

and of course besides the crank grooves for the rear rope seal era of engines-----there is issue of waterpump if they use automotive pump------

Generators might be issue IIRC but alternators will work either direction

And of course-oil pump and distributor