Whitebear- That Slick 50 stuff is something I am been impressed with.
I knew someone that had new boat with a ZZ3 and ran the tar out of it. Got her hot due to cattail seeds on the radiator. Not too hot, but hot. Motor developed a knock, real loud and steady. Well the owner was not the best mechanical understanding fellow and one of the old timers told him he had something wrong on #3 or #5 cylinder. He laughed it off.
He was running his boss around about 4 days later and bam. Connecting rod on #5 cut loose. He heard the noise and looked back, claimed there was nothing in the back of the boat (thought it was trash the PW ate up) and kept going. His boss didn't like the sound and kept looking back at the bottom for trash, finally looked back at the rudders and they were painted black.
Piston had smashed the spark plug and bent a valve, connecting rod hit the side of the cylinder sleeve, took a chunk out of it, sliced the oil pan open and all the oil blew out.
Well they ran the boat in about 5-7 minutes of running and dry loaded the trailer. He almost got his A$$ whipped because he did that in the parking area and at least two other boat owners were there and saw him sandblasting the vehicles in the launcher parking area (Gravel lot- I would be mad to).
Engine turned over easily by hand with the plugs out. How does a motor run that long without oil pressure? Only thing I could think of was the slick 50.
P.S.> That cat popped another engine about 9 months later and no longer has an airboat, some people just don't need to be running airboats.