I recently replaced the water pump with a Yamaha kit. Followed the instructions in the Clymer manual. I did not find any major problems with the old parts but the impeller and wear plates were a little worn. I decided to replace all the parts with new parts from the kit. I also cleaned the popit valve as recommended by rodbolt. I also checked the calibration of the pressure gauge. It was accurate. After test running the boat, the idle pressure was 3 - 4 psig. As I accelarated to get on a plane the pressure increased to 21 - 23 psig. On a plane and 5000 rpm, the pressure slowley decreaed to 15 psig @ 5000 rpm. It ran this way for 15+ minutes with no temperature alarms or problems . My question is this, when the motor was new, the pressure was always 20+psig at 5000 rpms and now it only runs at 15 psig. Is this the normal pressure for the system and is the gradual decrease in pressure after getting on plane normal? Thanks in advance.
