Beware of thinking simpler is better. That's how you wind up pulling the engine entirely.
The difference from 140F to 180F should not be a fire risk, even paper won't catch until 451F and that's a long way off. Heating the boat, yes, that's something else again. Poor insulation, poor ventilation, and no blower can all contribute to that. Even at 140F, you may want to run the blower after the engine is shut down, so it cools off the boat AND so it cools off the engine and prevents the oil from coking.
Or just pull the engine.
That was one of the problems in the VW Beetle, by the way. Air cooled engine, terribly inefficient. Simple, yes, reliable, maybe, but very inefficient.
I am not saying 180 F will cause a fire risk, but the hotter engine makes everything else in the engine compartment hotter. Things like the alternator, belts exhaust outlet, fuel in the fuel lines, elelectrical wiring and its insulation. The cooler these item run, the better for them and less risk of fire. I do not have a blower in my diesel engine compartment, and I do not think most diesels have a blower. I like being able to seal my boat up completely, should be able to take a roll over and only get some water in through from compainion way leakage.
Gasoline engines are required to have a blower, and due to lower ignition temp of gasoline, keeping engine and its compartment cool is even more important.
Air cooled engines are a whole nother ball game. Never liked them. Don't understand how one can maintain a constant engine temperature by blowing air. Never owned a volkswagon and even an air cooled porshe is just a glorified volkswagon- at least the air cooled models- on top of that, they sound like hell. My two cylinder lawn tractor sounds better than a 911. I always did like the look of the 911 Targa however.