How do I tell if my fuel pump diaphragm needs to be replaced? Early 70's 55hp magneto ignition, single carb.
If the pump is in good enough shape to start and idle smooth and run in the lower ranges fine but is not good enough for WOT running, how will it act? Would I expect it to just have a significant lack of power at WOT or should it be sputtering and missing?
I have no idea if it's original or not. I'm replacing it regardless, just trying to determine if a weak pump is causing my top end power loss problems or something else. It's the only thing I haven't been able to rule out yet but my thoughts are that a weak pump would just cause the carb bowl to be sucked dry at WOT and it would start sputtering. I don't have the typical starving symptoms, but acceleration just hits a brick wall above 3/4 throttle.
BTW, where do you get one for $5 at, the cheapest I can find is like 17 bucks.
If everything is correct, maybe you are expecting too much out of the motor. If the RPM's are there, the load may be too heavy, the prop may be the wrong pitch. Sorry, I'm out of suggestions. Maybe Frank will chime in.