Motor is 1989 Johnson 9.9. Since I do a lot of trolling with this motor I change spark plugs often, usually 3 or 4 times a year. When I went to change the plugs the top spark plug didn't have any of the electrod left and the bent peice of metal where the spark hits was gone also. Motor was running fine and how long the plug has been this way I don't know but it has been in the motor for at least 2 months with every day use, at least 5 hours per day. The plugs are the correct size 77JC4. Since the motor is older and has a lot of hours on it, I don't want to spend alot of money getting it repaired, is there any way to check to see if the broken parts are sitting on top of the piston? I put new plugs back in and it has ran fine for the last week and a half. Still purrs with no noise coming from the motor other than the normal noise. Could it have been that the plug tip just burnt away?
