9.9 yamaha losing prime

[wwobbley]

i have a 1993 9.9 yamaha that loses prime while running i pump it up and it will run fine then all of a sudden if i dont pump the ball it will stall when this happens the ball is soft and it seems it is starving for gas i changed the fuel diafram and it still does it any ideas????

[jb123]

ensure you have no air leaks in your fuel lines/fittings and be sure your tank is vented,not clogged. does your ball collapse? try using another tank to isolate your issue.

[wwobbley]

the ball does not collapse and the main motor which is 150 hp yamaha runs fine off the same tank which is a 90 gallon tank could it be a weak or bad diafram even though it was replaced at the beginning of the season last year

[grump]

I am having the same problem with a 1997 9.9 high thrust.After you prime up the motor it will run fine and it will slowly start to sputter and die . If you pump up primer bulb it will run fine. New primer bulb assy. and fuel lines.I took the fuel pump apart and there where no holes in diaphram. any ideas?