merc 40hp no top end power

[eaglewalking]

I have a Merc Mariner 40hp 2 stroke that has no speed at full throttle. At full throttle it will only turn about 2500 rpms. Without a load (not in the water) it will rev to the limiter. My son and I suspect the CDN module is no good. The modules sparkplug has a lot of unburnt fuel on it when we remove it after testing. The other module sparkplug looks fine after testing. Are we on the right track or completely out of the water? Someone please help! Thanks

 

[crappiejig]

Re: merc 40hp no top end power

I am sure you checked for spark on both cyl, what were the results?

 

[verado7]

Re: merc 40hp no top end power

ignition wires can cause this too - i know from experience and i'm really good at touching the wires while standing in a puddle - zap.

 

[chrishayes]

Re: merc 40hp no top end power

im surprised the muff police didnt site you for running your motor to the rev limiter on them. I would suggest not doing that unless your in the water. you could end up with the problem I have. Scored pistons!