Re: lost
If it's sucking the bubble shut, then you have an obstruction upstream of the bulb, or else the tank vent is closed or blocked, or else the bulb itself might be faulty.
If your boat has a built-in tank, it might have an anti-siphon valve, usually located where the fuel line meets the tank. When an inboard engine's fuel inlet is below the fuel level in the tank, and a leak develops (carb float valve for example), fuel will siphon out of the tank and flood the engine compartment and you won't realize it till the bilge pump kicks on, or you try to start the motor, or otherwise generate a spark.......
But, the anti-siphon serves no useful purpose with an outboard, as the motor end of the hose can never be below the tank -- siphoning is a physical impossiblity, as it would violate the law of gravity. You can take it out & throw it away.
Since you've ruled out all the other possibilities, you probably need a new bulb.
