I have a 1960 Mercury 300 that I just bought and it doesn't seem to be getting fuel past the valve that comes off with a quarter turn. There's fuel going up to that valve, but not past it. Could it just be stuck, or does it need replacement?
Could possibly be an air pocket. Try moving the tank above the engine. It could also be that your fuel pump diaphram is weak and cant move fuel past that point, you could try replacing that also. I would take apart the carb and make sure there is no restrictions. There is probably and internal fuel filter in there also that will get gummed up with old fuel.
Not getting fuel...
