1981 Merc 70hp Bogs down and dies over 1800 RPM

[trendsetter240]

I have a 1981 mercury 70 HP, Long shaft, remote, electric start made in canada model. This engine starts and runs great at idle but out on the water in gear it will bog down and die as you try to accelerate past about 1800 RPM.

First things first, I've replaced gas tank, gas line and primer bulb, fuel lines in the motor, fuel filter and thoroughly cleaned carbs. This did not resolve the problem.

Next step was to check the stator and trigger and both are fine.

Any ideas on where to go next? The local merc dealer thinks it's not worth spending anymore time or money on it. Seems a shame to let this one go as it's in good overall condition and up to about 1800 RPM is a perfect motor.

 

[trendsetter240]

Re: 1981 Merc 70hp Bogs down and dies over 1800 RPM

Still have this issue...

Could this be caused by a blown lower crank seal? That was one suggestion I had from a marine mechanic. That's a pretty big job to do on speculation.

Also I'm thinking that maybe this could be caused by the diapham behind the fuel pump..any thought?

Another note is that if you pump the ball on the fuel line while accelerating it does not solve the problem.

any advice is greatly appreciated.

cheers.