Old Mercury 3.9 sprays gas out of carburetor cover when priming

[cxgibson]

Hi everyone. I google my little heart out but didn't find an answer so I am asking you. I recently got an old Merc 3.9. It runs OK, but when I prime it or just run it in general it sprays gas out of the hole in the carb cover that I have indicated in the attached pictures. I have no idea why this hole is there or what it is for. It is just a through hole with nothing to block it to prevent fuel from leaking out when the bowl is full. Is there supposed to be something there? Fuel also leaks out every time I tilt or otherwise move the engine. Thanks!

 

[racerone]

Pretty simple.----There is an issue with the float or the float valve.----Too much fuel is being let in.-----And that hole has to be there.----The fuel in the carburetor bowl needs atmospheric pressure on it while running.----That is how carburetors work !-----Do not even think of plugging that hole.----And yes I can sound blunt to a novice.

 

[cxgibson]

That makes sense. I have disassembled, inspected and cleaned the carburetor components. The needle, float and seat are all in very good condition and it seems to be seating fine. Is it possible that the pressure from the primer bulb from the fuel tank is easily overcoming the needle seating pressure allowing fuel to enter the already-full float chamber thereby forcing the excess fuel out of the breather hole? I was thinking about some chainsaws that I've owned and how you could prime it until you were blue in the face and the excess fuel would go back into the fuel tank through a very small hose. In this case, is the excess fuel just dumping out and is it just something I will have to live with? It doesn't seem to leak any fuel when running, just when I prime it or tilt the engine allowing the vent hole to become lower than the fuel level. Thanks for your reply.

 

[racerone]

Correct an able bodied individual can generate much more fuel pressure than the pump on the motor.----You will learn how much to squeeze the manual fuel pump.----It just needs to fill the carburetor so you don't have to use the recoil starter to do that.