mercury 7.5hp fuel issue please help

Hey guys/gals. I have an early 70's mercury 7.5hp 2 stroke outboard. Once I start it and take off it runs like a striped *** ape, but after about 10 seconds it starts sputtering and will die if I don't throttle down. I noticed that once it starts doing this I can squeeze the primer bulb and it isn't firm. I can squeeze gas into it and it picks back up again. It seems like my fuel pump isn't keeping up but I have rebuild the carb and pump and it hasn't changed anything. Please help boat season is among us!

 

Try elevating the tank for a gravity feed test, if the problem still the same, it would suggest obstruction somewhere along the line.

 

I tried that too but it still doesn't run any hotter than half throttle and I have all new fuel lines. I just have my line ran into a plastic jug would that be the problem ?

 

Needle valve in carb not sticking ?

 

have u tried another squeeze bulb. if the check valve in the bulb is leaking back you will have the problem u describe. how fast does a stripe assed ape go .

 

Maybe the bulb is only allowing fuel through under pressure. Whatever the case, should try another one.

 

Idk how fast it goes hut it moves my little boat pretty quick. But I feel like the fuel pump is either really weak or I have an air leak somewhere.

 

How does it run with the cap off of the gas tank? Clogged vent?

 

It runs the same, the fuel can is vented well. Does it need to be a boat fual can or can i just have my hose going into a 5 gallon jug?