Mariner 8hp w Marathon only firing bottom spark plug

[Mercruiser 120]

Serial # 677-364773
My dad’s Mariner on the back of his sailboat always has run great. Started to lose power and just run on 1 cylinder. The top spark plug was always wet. He boat a new secondary coil(nice grey one, attached on the outside of the motor with wire going to spark plug). Put it on. Fired it up. No change.
There are points and coils under the flywheel. Is there something we could check before we take the flywheel off. Thank you

 

[Mercruiser 120]

This is the Flywheel on a mariner 8hp but is a Marathon with a special Flywheel. Do we need a puller to get it off

 

[pointblank1000]

Sailboat??
Been in saltwater?
I would check EVERY electrical connection before anything else. Salt destroys everything.
Pulling the FLYWHEEL requires a 3 bolt puller. Buy it at harbor freight.

 

[Mercruiser 120]

Sailboat??
Been in saltwater?
I would check EVERY electrical connection before anything else. Salt destroys everything.
Pulling the FLYWHEEL requires a 3 bolt puller. Buy it at harbor freight.

Thank you for answering. We are up in Canada, no salt water. But good tip.
It is a special motor. It has 4 coils, two with the magneto and two exterior. It actually charges the battery to run other stuff while it is driving.

Mariner W8 (M) (W / Marathon) Flywheel Magneto Parts

Mariner w8 (m)(w/marathon) flywheel magneto parts. Buy a genuine Mercury Quicksilver or aftermarket part.

www.marineengine.com

Here is a diagram

 

[Mercruiser 120]

So we know that the exterior coils are ok. I ohm tested them. My dad is impatient and he bought new one’s without telling me. Still no spark to top cylinder.

 

[alldodge]

Looks like a 3 point puller would be used to pull. Need to get to the points.

Maybe @Texasmark or @Faztbullet

 

[Faztbullet]

Use a puller but just runs bolts in about 1/4 inch as to deep you can damage items under flywheel and the bolts are metric.