100 LL AVGAS my friend. Take a 5 gallon jug to the little local airport and get it for your airboat.
Love to, but neither of my motorcycles will run for crap on 100LL. Like many engines, they will start having harmful deposits form in the combustion chamber (and elsewhere) if you run more than 87 octane in them as they are optimized for that grade of fuel. Can’t use it in either of my gasoline powered cars due to their catalytic converters and my truck is (fortunately) diesel.