Mechanical fuel pump arm not being activated by cam

[rcwhee2]

1982 Bayliner Capri, Mercruiser 140 HP, Serial # 6045105. Boat had an electric fuel pump on it when I bought it. I noticed that the gauges acted up when the fuel pump was running (kneeled would bounce around) I also noticed that the original mechanical fuel pump was still attached to the engine. I removed the electric pump and bought a new Sierra 18-7278 mechanical pump. The new one looks identical to the old one. I noticed that when I installed the new pump, that the cam inside, does not seem to reach the fuel pump arm. I also noticed that when I removed the old one that there was no tension on the arm. Does anyone know if there is supposed to be a push rod on this engine that is missing or do I have the right fuel pump? Alternatively, is there a good marine approved electric fuel pump that will work on this engine?

 

[Scott Danforth]

Arm rides on cam on the inline motors

 

[stonyloam]

Yeah sounds like your pump lobe on the cam might be shot. Some of the folks here have used the Airtex pump, 2.5-4.5 psi. In addition you will need an oil pressure switch, a T to plumb it into the oil pressure sender and an electric fuel pump relay. You wire it so that the pump runs when the starter is turning, and when the oil pressure is up. Should you lose oil pressure the fuel pump will stop. Here is a diagram post # 8 https://forums.iboats.com/forum/engi...ressure-switch. That diagram shows the pump running directly off of the switch, however you would want the switch to activate the relay (red wire) which would turn on the pump. The relay contacts will handle the electrical load a lot better then the switch contacts.

 

[rcwhee2]

Thanks for the info. Regarding the electric solution, I have been told that the fuel pressure needs to be between 6 and 8 psi for my motor. Earlier I had tried to use an over-the-counter 4 to 7 psi fuel pump from oreilly’s auto parts. That pump did not seem to supply enough pressure at higher rpm’s. I could only get the boat up to 20 mph and the RPM only up to 3400 at full throttle on the water. Does anyone have a make and model of a good Coast Guard approved marine pump?