I recently bought a boat that came with an 81 johnson 115. It has a melted piston but I'm sure could be rebuilt. However, the guy included another johnson 115 that he got on craigslist that doesn't have a lower on it. He was going to swap the lower from the damaged motor but it wouldn't bolt up on the other johnson. I don't know what year the spare engine is as I cannot find any model info on it anywhere. It is definitely newer than the 81 that is damaged just based on looking at the motor. It has a newer type of ignition system than the 81. My question is what years are interchangeable as far as powerheads?? Can I swap the newer powerhead onto the 81 mid and lower units?