Nathanboater
New Member
Hi everyone,
I just recently bought my first boat and motor. The motor is a old Mariner 4M 6E0 S 083659.
The motor has ran pretty good ever since I bought it. Decided to do some preventative maintenance and changed the spark plug so I could keep the current one as a backup.
To order the plug, I took the old one out which was a NGK BPR7HS 10, so I bought a new one using the same code. The plug looks the exact same as the one I bought but when I put it in the motor (torqued to 24NM), the piston hits the ground electrode on the spark plug and bends it over.
The piston stroke is perpendicular to the spark plug hole. I noticed that if I threaded in the plug so that the ground electrode is on the opposite side of the piston , then the plug doesn't get hit and the motor runs fine, the problem is by rotating the plug the one way I can't tighten it down.
For now I've installed the original plug but it works because when torqued the ground electrode is on the opposite side of the piston.
This all makes no sense to me as I have never heard of a plug having to be a certain direction and this makes me think my motor is having issues, but since it runs great I'm not sure.
I can't figure out the model year using the motor serial number and also can't find a manual. Maybe these aren't even the right spark plugs?
Does anyone know anything about this?
I just recently bought my first boat and motor. The motor is a old Mariner 4M 6E0 S 083659.
The motor has ran pretty good ever since I bought it. Decided to do some preventative maintenance and changed the spark plug so I could keep the current one as a backup.
To order the plug, I took the old one out which was a NGK BPR7HS 10, so I bought a new one using the same code. The plug looks the exact same as the one I bought but when I put it in the motor (torqued to 24NM), the piston hits the ground electrode on the spark plug and bends it over.
The piston stroke is perpendicular to the spark plug hole. I noticed that if I threaded in the plug so that the ground electrode is on the opposite side of the piston , then the plug doesn't get hit and the motor runs fine, the problem is by rotating the plug the one way I can't tighten it down.
For now I've installed the original plug but it works because when torqued the ground electrode is on the opposite side of the piston.
This all makes no sense to me as I have never heard of a plug having to be a certain direction and this makes me think my motor is having issues, but since it runs great I'm not sure.
I can't figure out the model year using the motor serial number and also can't find a manual. Maybe these aren't even the right spark plugs?
Does anyone know anything about this?
