2000 F80 losing rpms

[Jackfish]

My 2000 F80 four stroke starts on first key turn. It runs great while at idle. It runs great on initial acceleration and gets up on plane. Then after about 20 seconds I lose rpms and it sputters.

I have replaced gas tank and line up to fuel separator , fuel filter, fuel water separator, spark plugs, impeller and thermostat with little to no change.

Looking for quality advice on my situation. Thanks

[boscoe99]

I see a whole bunch of stuff that has been changed which would not be up at the top of the list of problem areas for what appears to be a fuel starvation issue.

I don't see any mention of the fuel pump having been changed.

If you have someone continuously pump the primer ball when the motor is getting onto plane and as it runs, does it sputter or does it then run well?