As per my earlier post, I have a mid - late 80s Reman 200 merc on a 150 mariner 150 mid. 1.87 gear lower. It had the top starboard piston melted with a hole in the center. Got it split, and ready to rebuild, but cannot find a reason it blew. I expected to find plugged jets, stuck float.. something, yet I found nothing. I'm going to replace water pump as a precaution. I have the wh-39 carbs. Are these the proper jets?
Any ideas as to why she blew? Other 5 cylinders look great. Perhaps old fuel and too far advanced timing?