Serial # 1B539432 I changed plugs, motor ran fine ( 170 hr.s ) , next trip started only running 5200 rpm tops. Mechanic said plugs not gapped right, all carboned up. He changed plugs. Next time out motor did same thing, now the mechanic is trying to figure out why motor is apparently over oiling..... I bought boat and motor new, only problem until now was 2 bad Coils.....serial number.