Yamaha 1999 C115 pre-mix carbed engine. Motor suddenly started running rough recently...it idles and runs (not under load) smooth enough but coughs occasionally and blows a puff of smoke. I replaced the spark plugs, installed new fuel filter cannister (no water), serviced the fuel filter at...
Motor is maintained like an aircraft...300 hours. Was out fishing for several hours and then tried to get up on plane and run at normal high speed. Motor started sputtering and missing, barely made it back to the ramp. Pulled plugs (only 15 hours on them) and they looked OK...cleaned...
