Mercury 4 cylinder Fuel pump??

[Lostfisher]

I was running a merc 4 cyl 650 with 2 carbs and noticed that it started to bogg down a little. So i squeezed he primer ball and it was soft. I was able to squeeze it several times before it got firm. After a few squeezes the RPM's did pick up and the motor went back to a nice idle. I was told that it could be several different things that cold be causing the problems. Problems with my lines, dirty filter, bad fuel pump, etc. So I took out the filter and they were both nice and clean. Now my I am able to run the motor at a higher throttle with no problem but once I bring it to an idle and leave it there for a minute or two it starts to bog and stall out. Does this sound like a fuel pump problem or something else???

 

[CharlieB]

Re: Mercury 4 cylinder Fuel pump??

Sounds more like air sucking into the fuel line somewhere between the tank and fuel pump.

At idle the pump is moving more air than fuel.

A common fault is the o-ring in the coupler fitting, when you squeeze the primer it will seal but when the pump 'pulls', it sucks in air.

Install a temporay clear hose between the fuel pump and carb, watch for air bubbles. Remove the clear hose once finished with your repair.

 

[Townes]

Re: Mercury 4 cylinder Fuel pump??

not trying to hijack the thread however...great advice CharlieB. I had the same problem only much worse (no fuel to lower carb/horrible idle). Removed the coupling and found the o-ring wrapped around the spring. Easy fix.