85 merc 75 fuel leak

I have a 1984 (whoops made a mistake in the title) mercury 75 4 cylinder and have a fuel issue. I just purchased this motor. It has sat for a few years. I discarded the oil injection system and hooked up the tank to the primer bulb to the motor. When I try to pump the primer bulb it will not get hard.

When you trace the fuel line it goes to what the Seloc manual calls the fuel filter. The fuel comes into a circle shaped fitting with one screw in the center. That fitting attaches to the filter and has an o -ring between. I replaced the o - ring with the closest I could find at a local auto parts store. There is still quite a bit of air and some fuel that leaks around the edge of that fitting which attaches to the filter. Every time you squeeze the bulb it leaks.

Any help with why the fuel fitting at the filter is leaking would be appreciated.

Dwight

Re: 85 merc 75 fuel leak

u need the correct merc oring, the ones at the auto stores are to fat and will just squeeze out, not that big a deal until your engine burst into flames.

Re: 85 merc 75 fuel leak

That round filter is the front of the fuel pump.
Pics of the o-ring?
Inside the pump is a diaphram,it could be ruptured???
Take it apart and check the whole pump.
Ethanol is messing with old hoses and connectors.
Replace the whole unit if the parts are too hard to find.
They put 2 different pumps on that model,
sounds like yours is the older rectangular style.
This might help.

Mercury part # 35480
"O"RING, COVER TO FUEL PUMP $1.67 $1.16

Mercury part# 55278A 5
DIAPHRAGM ASSEMBLY $5.10 $3.57

Re: 85 merc 75 fuel leak

Rebuild the entire fuel pump. A rebuild kit will have all the gaskets and seals, and costs only a few dollars.

Re: 85 merc 75 fuel leak

I don't have pics of the o - ring.... but it fits right behind the circle fitting in the center of the first pic.

It's not the triangle it's the rectangle style filter/pump.

I think it's weird that before and even after when I installed the automotive o ring it still leaked around the edge hi-lited around in the second pic. Although the automotive one is obviously round and the merc one is flat on the edges. The old merc one doesn't look perfectly true anymore.

Has anyone seen it leak around this fitting before???