nitrousnolan

Ok, I have a 93 35' Fountain, I have Xr's w 2" Imco shorties, Stelling boxes w the drive mounted in the top position of the box. Over all 3.5" above the stock X dimension, I have the Mercury ByPass Valves for the water psi also. All these parts and motors are 100% new prob 6-8 hrs on total package. This weekend at the Kingston Run I noticed at 4000rpms my water psi was running at 35 psi on the gauge, I back down to 3000rpms and it went to 18 or so and at 3500 it would hit 25psi then drop to 20 psi as they should since the merc bypass works at 25 psi......correct???? Any ideas or insight is appreciated, Thanks