Another fuel pump question

[Georgebfp]

I have a 99 5.0 Gi. Throttle body. Boat ran perfect Thursday. Yesterday as soon as I put it in the water and throttled down, there is no low end horsepower. It struggles and gets up on plane. There was a whining sound Thursday. There's one fuel pump in front and one on the back of the motor. Can one pump be bad and it still run. Any suggestions?

 

[gbeltran]

Yes one can be bad and it will run. Which one is whining? I would say it's most likely the low pressure pump.

 

[Georgebfp]

I think the one toward the back. It's not whining anymore. I'll have to look at the repair booth to see if it's the high or low