Sounds like you got something that is not OEM. Should have simply bought a gasket/diaphragm kit and rebuilt your original pump. Can't go wrong that way. It's the gaskets and diaphragm that goes bad not the metal housing.
Have somebody drive while you squeeze the primer bulb when trying to accelerate. If that has an impact look closely at the fuel pump. You state you replaced the fuel pump. Normally people install a rebuild kit that's gaskets and diaphragms.
The idle timing spec is not that important. That's why it's given as a range. It's to only get you in the ball park. The actual timing spec is one that makes the motor idle at the proper RPM. My 1988 Mercury manual states the 90 hp should have the idle timing adjusted to make it idle 650-700...
Yes. There is a small filter on the accelerator pump output. It's on fuel line going from the pump to line that connects to the #3 and #4 cylinder check valves. But there should not be an issue with that filter. Not much can go wrong and the amount of fuel going through it is minimal. I'd...
The accelerator pump is completely different than the enrichner. Also this motor's accelerator pump is not a part of the carburetors. It's a separate diaphragm that is throttle linkage actuated and plumbed to the bottom two cylinders.
I would agree there should be no difference in holeshot but there was. The gapped ones just did not hit as hard. No doubt about it. Not sure why.
Also, the enrichner sends gas to all four cylinders for starting on this motor.
The factory recommended spark plug for that motor is NGK BUHW which is a flat gapless style. At one point Mercury was recommending changing to a regular gapped automotive type plug. I tried them and found the engine did not have the same holeshot and went back to the BUHW's. Maybe the gapped...
That may be normal for that motor. The many smaller motors were designed with lower compression to make them easy to pull start. That's about the same comp number as my old Johnson 3 hp. Even brand new they were only about 60 PSI
