75 Merc 8500 fuel leak at carbs\air in the line?

[tompowers85]

I have a problem. I have fuel leaking from my carbs and i have replaced everthing but the fuel tank. I am getting air in the lines some how. If my tank is not holding pressure will that make a difference. I have plugged the vent and prime the bulb and it only stays hard for a minute or two, and when i prime it again my carbs start pooring. I cannot think of what to do. I rebuilt the carbs i have set and adusted everything several times and i cannot get the problem fixed. I have an aluminum 18 gal tank that cam with the boat and it is about 30 years old it does not leak fuel, but if their is a broken weld around the vent or fill tube can that cause a problem.

 

[Ben Konopacky]

Re: 75 Merc 8500 fuel leak at carbs\air in the line?

did you change the neenle valves and seats w/new gaskets, also adj. float.. don't put a lot of press.on the preme bulb (5# max.)on the seat otherwise it will leak into the carb.as far as air goes check all fuel line connections use tye wraps if you have to..

 

[tompowers85]

Re: 75 Merc 8500 fuel leak at carbs\air in the line?

I replaced the needle valves and seats i have done everything. How long should the primer bulb stay hard?

 

[Bob H.]

Re: 75 Merc 8500 fuel leak at carbs\air in the line?

Sounds like you're squeeezing too hard pushing the needle valves out of the seat. You'll probably need to adjust the floats again. The primer bulb doesn't need to hard, only firm enough that you can feel there's fuel in it. The check valve in the primer bulb won't hold pressure too long, it doesn't need to. Once the engine starts the fuel pump will keep the carbs full.