57 johnson 10 hp fuel line pressure.

[aed fishman]

have replaced diaphram, fuel lines and check tank for leaks. it still wont keep pressure when running the motor. What next?

[oldcatamount]

The fuel/air connection (at the motor end) may have a bad o-ring, or the fuel tank cap could have a bad gasket. How did you test the tank if it didn't have pressure in it?

[Chinewalker]

"Replaced diaphram" - in the pressure tank? Or has this motor been converted to a fuel pump?

[aed fishman]

The fuel/air connection (at the motor end) may have a bad o-ring, or the fuel tank cap could have a bad gasket. How did you test the tank if it didn't have pressure in it?

I pumped it up, put it in tub with water to cover it. i found a small leak and sealed it with indian shalach. i havent replaced the fuel tank cap. I replaced the diaphram about 5 years ago.the engine stops running unless I keep pumping the pressure up.

[F_R]

So...you have two systems involved here, the tank and the motor.

The pump in the tank (button and diaphragm) pump fuel to the carburetor so you can start the motor. The tank pump does NOT pressurize the tank. A running motor pressurizes the tank. So your method of "pumping it up" and putting it under water is invalid if you mean pumping the button. Howeer, yes you can pressurize it with compressed air through the air hose.

Get your motor running and keep it running by pumping the button if need be, for a couple of minutes. Stop and loosen the cap. You should get a hiss as pressure escapes. If not, there are two possibilities:

1. The tank is leaking. Or the fuel connetor o-rings are leaking. The solution is clear--fix it.

2. The motor is not pumping air. That is accomplished by a couple of rubber check valves in the intake manifold. I've seen them turned to mush. OR, the air hose is busted. Otherwise, there is nothing that can go wrong with the motor's part.