Irun a 90hp johnson,the champion plugs seemed to foul out quicker. 10 years ago i switched to AC Delco plugs M40FFX.This ac plug is a direct cross with theCHAMPION. Motor ran much better one set of Ac's per season. My buddy has a 75h.p. Evinrude same problem w/Champion,swiched to the Ac plugs 100%better .Both are two strokes.The 90 h.p. had acomplete rebuild 12 years ago.