Why is the fuel line bulb of my Yam 50 hp outbrd colapsing, creating presure so fuel doesn't flow?

Question

Vent on tank is open and clear. With engine running as presure builds it cannot suck enough gas. I can undo fuel line from tank to release enough presure and gas flows until the presure builds again. Take about 1 minute for the presure to build colapsing the primer bulb.

Answer 1

It can only be a few things. the vent, even if you say is open could be clogged, the fuel line or the bulb is clogged or collapsing. If this is a portable tank run it with the cap off and see if it runs. If it does it is the vent. If its a built in tank the vents can still get glogged from the outside and again you can try it with the fill cap off to see if it still runs. Try replacing the bulb after you have checked the vent. If thats not it replace the fuel line. Old fuel lines can get soft inside, especially with ethanol.

Answer 2

I believe that your fuel pick-up tube is blocked or clogged.

Try running from another tank.  If it runs okay and you are sure that the vent is clear - replace the pick up tube.