high speed miss help!!!!!!!!!

[008wagon]

i have a 1989 johnson 60 horse. when running full throttle for 10 to 15 minutes the motor will miss/buck like it is losing all power ,then the power comes back in a split second it doesn't always do this though. last year it did it and i had a power pack and all three coils replaced now it doing it again any ideas? the compression is 105 to 110 psi on all three. always use seafoam in the gas too. thanks

 

[1946Zephyr]

Re: high spped miss help!!!!!!!!!

Re: high spped miss help!!!!!!!!!

It sounds like a fuel issue. Your fuel pump may be getting weak and not keeping up with demand, or you might have a fuel flow issue in your lines.

 

[renegade15]

Re: high spped miss help!!!!!!!!!

Re: high spped miss help!!!!!!!!!

Have you checked timing? I had a similar issue with my old engine and it was that the timing was way advanced. I think that is what finally led to the piston detonation

 

[Cofe]

Re: high spped miss help!!!!!!!!!

Re: high spped miss help!!!!!!!!!

Being that it is a 1989, the fuel lines could be deteriorating, and loose rubber particles temporarily restricting the high speed circuit in the carb. You should replace the 22 year old fuel lines.