75 hp merc only 3000 rpm wot in gear

[rednekbowfisher]

I have an o3 75hp merc ran great then the crank case hose which run to the fuel pump split replaced hose, may or may not be related. All of a sudden the boat will only run 3000 rpm at wot under load ( motor is on party barge) there is no misses or hesitation but will only get 3000 rpm. Now if I fast idle it at the controller boat revs up just like it should, any idea this one has got me puzzled. all cables and rods are getting full throw and this motor has never been touch or adjusted ran fine the day before

Thanks Jason

 

[DuckOfDeath]

Re: 75 hp merc only 3000 rpm wot in gear

I'd check for good spark on all cylinders as my first step. If that looks good, verify compression and check the fuel system. Could be as simple as the gas tank vent being closed.