Merc Fuel problem

[JM4]

I have a 1967 Merc 950ss that seems to be starving for fuel.
It runs about 5 minutes without manual recesitation. I have to manualy pump the primer bulb to keep it running.
Here is a list of the Maintenance performed in this order:
Made sure the fuel tank vent is open.
Replaced the fuel line and primer bulb with a "Bass Pro Shop" Merc replacement.
I have rebuilt both fuel pumps "diahpram & gasket" and replaced all the check valves.

After this MX has been done, the motor still only runs for about 5 minutes before dying.
The primer bulb has once again become spongy. No improvements have been made. :facepalm:
I am a rookie when it comes to marine motors so any troubleshooting help would be appreciated.

Regards,
Boat missing the water.

 

[bgc]

Re: Merc Fuel problem

I found the line feeding from the cowling to the pump had an air leak on mine. It was the swivel at the compression fitting.

 

[JM4]

Re: Merc Fuel problem

I dont see a swivel connection on the line that feeds the 1st "lower" pump.

 

[bgc]

Re: Merc Fuel problem

Sorry, swivel connection is bad terminology. It should be a small brass compression fitting that holds the fuel line onto the fitting at the pump intake. Inside this fitting is a small cylindrical gasket that could be the source of the air/vacuum leak.

 

[CharlieB]

Re: Merc Fuel problem

Primer hose quick connect to the motor often leak air into the system. Many remove the whole fitting assy and run hose staight in to the pumps.

Test by temporarily installing a clear hose just before the carbs, watch while running for any air bubbles passing thru. Remove the clear line once repairs are finished.

 

[JM4]

Re: Merc Fuel problem

What do they always say.....start with the easy stuff? Found the pickup tube deteriated and laying at the bottom of the tank. Nothin like trying to drink a soda through a 1" straw.