mid 70's 20hp fuel issue

[Rjack]

Hello folks (new to the forum), I have recently purchased a mid 70's 20 hp mercury outboard. It runs, starts, idles, fine. I found a cracked fitting that was leaking gas and I had the fellow replace a few fittings and lines and at that time I was told that if the primer bulb is over pressurised the gas would flow out of the carb, and indeed it does. My issue is that with the gas line connected and the vent closed on the tank, there is a build up of pressure enough to push the gas out of the carb and into the boat/Lake.

Not being mechanical I was hoping to get some advice weather this is to be expected or what the problem might be so I can have the issue repaired.

Regards
Ron

 

[Scott Danforth]

open the vent. should be open all the time motor is in use

 

[Rjack]

thanks Scott, so the vent should remain open at all times when fuel line is connected to the motor even when not in use (overnight). As you can tell this is my first experience with outboard motors.

Cheers
Ron

 

[Scott Danforth]

yes, however the needle and seat in the carb may need to be replaced as well. it should hold back about 5 psi