if it didn't run very long or at too high an rpm, could only need a touch up on the seat and some new valves-it it broke and pieces got hammered between the pistin and combustion chamber-could get nasty----------180 manifold - pieces could cross over to other side probably to the end cylinders on that side-lucky you didn't have stainless nut/stud as magnet wouldn't work plus iron heads would be probalem also
good luck, I'd pull both sides to check every thing out-after all an air boat the engine is pretty open????????