TOPIC: 25hp

hi, i am working on a 1996 25 hp for a friend, he has had an issue with it stalling, he replaced the fuel pump diaphram and gaskets and still has the issue. i have it here in a tank of water and it starts easily idles good but even at a high idle it runs out of fuel and stalls, when i pump the ball it starts right up again. i know the tank and fuel line are good it is mine and i have had no issue with my motors. i even connected the fuel line directly to the carb to eliminate the fuel line connector. the check valves were not relaced but look ok. the passageway in the carb that goes to the fuel pump is clear and the reeds look ok, i thought maybe i could be losing crankcase pressure there. any suggestions? Thanks

I know this will sound too simple but is the gas tank vented? I've had issues with that, motor would run for a few minutes and then a vacuum sets up in the tank and no more gas flows. 1996 is considered a "new" motor for me but is the fuel pump run off the motor vacuum? Might have a leak in the vacuum line coming from the motor to the fuel pump.
Just a suggestion.

i think i narrowed it down to the check valve, i get air flow both ways when i blow into the fuel inlet.