Did I ever tell the story of how we melted an outboard? This was on a powerboat, not sailboats, but still.
We used to have a 70hp Mercury in-line 4 cylinder 2 stroke outboard. My uncle was supposed to maintain it. One time we were out, and the motor was running really poorly. My friend pulled the plugs to see what was up, because it sounded like it was only running on 3 cylinders. He found metal bits on the end of the top cylinder plug.
Turns out, in these in-line Mercs, if the water pump isn't at full strength, the cooling water doesn't make it all the way up the block to the top cylinder. It overheats, and the bits of metal were really aluminum sputters from the melting piston head. Apparently, my uncle was not having the water pump overhauled each season he had the winterizing and tune up done...
We learned this from my friend who had a 120hp in-line 6 cylinder Merc 2 stroke. His mechanic advised him to change the impeller every year, because the 6 cylinder motors are especially prone to this meltdown. After he towed our boat 4 miles, we also learned that the in-line 6s are prone to bent crankshafts, and thus complete engine rebuilds... I felt really bad, we used to ski the heck out of that 120hp... Damn powerhead used to stick up from his 16' boat like a shark fin. Sure, it wasn't rated for 120... but we stuck a 1/2" aluminum plate on the transom, and it was solid after that
