So...I let a friend borrow our 15 hp backup engine (1977 Evinrude 15704M) and he indicated it ran great for the first few days Then it started to run real rough and acted as if only running on one cylinder. After further investigation, this is what we found. The upper piston looks as if it started to melt and the head is showing similar signs. This engine has always run like a Swiss watch and has never given us any problems. I'm going to try to find parts to repair this unit. Any Idea what could have caused this? Any suggestions would be appreciated
