you could cool the engine by installing a water sump and a keel cooler 1"
copper line looped under and outside the hull.
as far as the rpm you need to watch it because you can over rev the engine
due as others have stated prop de-capitavation.
besure you install a flame arrester on the carb and make the motor box so
that you get plenty of air flow it will help with the heat exchange and to
keep unwanted fumes from building up.
you can install a wet exhaust if you put some form of pressure release on it
otherwise it will suck up water as soon as you kill the engine. otherwise
runn it out the stern and give it hell.