1999 Merc 15 hp four stroke high speed miss

[noflipside]

I have a 15 hp 4 stroke Merc, when it is under a load at or near high speed it starts to surge and hesitate, almost like a high speed miss. I have cleaned the carb three or four times and the high speed, pilot main jets are clean along with all passages etc. checked timing it appears good. Spark plugs have perfect coloring(lite brown), checked fuel pump all appears ok. no apparent air leaks in fuel line o rings or hoses. Vent on fuel tank open, getting good fuel. I have also check engine running with water muffs on, still does it. I am thinking it is electrical. Anyone with some thioughts on this.

 

[Star]

Re: 1999 Merc 15 hp four stroke high speed miss

Hello high speed,
I own a 15hp merc. That is not a miss!!! They have a RPM limiter in the electronics. It dumps the spark when you exceed 5800 rpm. On my 14' Starcraft I'm doing 19.5 MPH. Reprop with a higher pitch prop. you will lose low end push but can get slightly higher speed. I have tried to find a way around this, but I have been unsuccessful up to now.