1991 Johnson 25 hp spitting from fuel pump

[Toeboater]

Hello All. I'm hoping somebody here can help me with this problem. I bought this motor last year and just getting around to getting it ready for the water. I replaced the charge coil and power pack assembly, noting here that I had to replace the flywheel due to nearly having to beat it off because it refused to budge. Yup, had to resort to using heat and an air hammer after breaking at least 1/2 dozen number 8 bolts with the puller...but that's another story.
I also rebuilt the carb to OMC specs as well as the fuel pump. Installed new plugs and replaced all fuel hoses.
This motor starts and runs strong in gear in a test tank but spits rather violently after it warms up and unless it is running at a higher rpm, it will sneeze and die. The thing that puzzles me most is that when it sneezes or spits, it's not from the carburetor but from the small hole on back of the fuel pump where the pin on the spring loaded "push rod" pokes through. Manual recommends 1 3/4 turns out for carb mixture for initial start and I've been all over the place after that, chasing the sweet spot. Also, did not replace ignition coils since they seemed to check out with ohm-meter. I have ordered a new set of plug wires but I'm not convinced that will cure the problem.
Anybody have an idea what is causing this? I would certainly appreciate it.
Thanks

 

[kodibass]

Re: 1991 Johnson 25 hp spitting from fuel pump

sounds like you may have a leaking gasket, the fuel pump mounting gasket or a bypass port gasket. listen intently for the sneeze and zero in on that location, run the motor in almost dark condition and look at the area of the sneeze when it does look for flame/light. that will be where the gasket leak is.

 

[Toeboater]

Re: 1991 Johnson 25 hp spitting from fuel pump

Thanks for that kodibass. I'll check that. The fuel pump mounting gasket is new with rebuild kit but the bypass cover gasket is an unknown. Not really sure what purpose the bypass cover serves except to provide a place to tap the lower cylinder for vacuum to operate fuel pump. I can't get to the motor right now but now that you mentioned the bypass cover, I do know that the hole for the vacuum fitting is out of round since it came out when re-attaching the hose after mounting the fuel pump. I applied gasket sealer to the fitting when I put it back in but can't say for sure that it was an air-tight fit. If it is not, would this cause engine to spit back through the pump?