Could extra weight influence water pressure?

[Buckeye Nitro]

I have a 2000 Ficht Ram w/ model # E200FPLSSC, serial # G 04811957 on a 2000 Gambler Outlaw. Just purchased the boat and have had it out twice with a little less than 1/2 a tank of gas in it. Noticed the water pressure around 22-25 psi at 4200 rpm. Filled the tank this morning and noticed water pressure 15-16 psi from 4000 up to 5100 rpm. Could the extra weight of the gas be affecting this or do we need to check the impeller?

[ChampioNman]

Time for a new water pump kit.

[Buckeye Nitro]

That's what I figured, but I wanted to make sure since it changed so fast and the extra fuel was the only change we had made. Thanks for the help, getting a kit tomorrow.