I have the above motor and on the 3rd trip out this year while running fine the motor just quit. After getting towed back to the dock and taking the head off 2 cilinders on one side are scored and large deposits of what looks to be carbon are on the walls. I know this engine needs to be rebuilt but my question is; What could have caused this? The engine was running fine, no alarms or any sign of a problem. Is this common on Johnsons? and What would you do? Rebuild or go new? the engine is in a 21 striper w/a.Thanks for any help
rpm were around 5500 fuel was 1 winter old and stabilized (I hope... It was winterizied for me)( I did fill it up before taking it out) plugs were changed at start of season and beginning of last seasion can't recall what type but I put the proper ones and gapped per manufacturer specs.