1983 40 hp merc losing rpms at full throttle

[rustyh]

have a 1983 40 hp merc on a 16 ft mod v bass tracker same year just rebuilt carb and new neddle seat float impeller and gaskets also lower end unit oil change ran fine for 2 or 3 trips up river usually just putputing and a good blow out going up river and back down on the way back to dock started to gom ummmm ummmmmm ummmm every 2 seconds or so and would not get up to normal rpm thanks in advance for help
ps also at 3/4 throttle would run normal with no umm ummmmm

 

[Laddies]

Re: 1983 40 hp merc losing rpms at full throttle

It sounds like a fuel delivery problem, if the fuel bulb goes soft while it's acting up check the anti syphon valve in the tank and for a in tank screen. If it's not soft then have someone pump the bulb to see if that helps, if it does either the fuel pump is acting up or the fitting on the fuel hose is leaking, however usually if thats the problem you will see a leak when pumping the bulb. Let us know if this helps.