1991 Mercury 115 Outboard

[Cstafford1]

Hello I have a 1991 Mercury 115 oil injected outboard. Runs GREAT when hooked up to a hose and when in the water until I get to anything over 75 percent throttle. I will be flying down the river and it bogs down loosing rpms and then rpms go back up and then back down. They keep surging until I drop the speed down to a comfortable causing speed. About 35 MPH. Any advice to what the problem maybe . Bad gas? Any fuel additives I can use in the gas tank to maybe clean out the fuel system? Thanks in advance.

 

[GA_Boater]

Next time it starts to bog down at WOT, squeeze or have some one squeeze the bulb. It may be the fuel pump.

I doubt much stuff in a bottle will clean the fuel system. Some will help a clean system clean, but not actually clean it.

 

[racerone]

Test run with a known to be good portable tank and hose.

 

[Old Ironmaker]

I have the exact engine a few years newer. I also had the same issue and a new bulb solved the problem. Hop that's all your problem is.

 

[sullmate]

could be a bad stator