Model#7067 3D 70hp 3 cyl bogs/stumbles

[B Hastings]

Engine runs but stumbles, have pulled the carbs and cleaned. Use sea foam & seemed to help,problem is erratic. Won't pull skier & when stumbles won't plane out.Have fresh plugs in it Am I looking at mechanical or electrical ? Any help would be appreciated

[boats.net]

Sounds like you maybe loosing spark in one of the cylinders. Check for spark when it stumbles.