I have a '84 Evinrude 140hp VRO with a jet pump on it that blew again. Second time in 6 months. The top piston on the driver side broke a ring the first time. So I took it to a renowned builder in Nixa, MO. He put the pistons that have a thicker ring groove in and this weekend lost all power. Took the head off and the bottom of the piston is melted. What threw me is that it had a gapped plug in it. Don't these motors require a gapless plug in them? I know he changed blocks when he rebuilt it, but the motor is at the lake, so I can't get a serial # until next weekend. If I get the serial # will that tell me if the gapped plug is right?

Thanks,

John