Mercury 125 spark issue?? Need some help!!

[Mattc8821]

I got the same engine with similar issues
cannot exceed 4200 RPM when engaged ,In neutral RPM can get up to 6000 RPM,
I did replace my fuel pump kit few months ago and the hose from the fuel pump to the filter with regular fuel line without any bend on it as the original , I think this created a fuel restriction , replaced the fuel line with original and testing schedule this week end

Did you test this weekend?

 

[flyingscott]

Do.you guys realize that there is a service bulletin on those motors to not exceed 5500 rpm. This is because the.piston skirts break.. And revving to 6000 rpm in neutral is just dumb.

 

[Trophy125]

Tested the engine this weekend ,no changes at all , i m just gonna use it this summer , no more money spending
MAX RPM 4000 ,speed 27mph

 

[Mattc8821]

Solution to my problem was a bad check valve on cylinder 4. I unscrewed the two check valves from the block connected to each cylinder (cyl 3 and 4) and found that #4 was dirty and being held open. After cleaning out and reinstalling, I saw 5200 rpms for the first time since this issue started. Spark plug color looks good also.