Still loosing water pressure
 

Still loosing water pressure, around 15lbs at WOT. I have around 22 lbs or so at 3K. Backflushed the entire system, flushed back through the drive, checked thermostat, etc. New cric pump and impeller begining of the season, pulled raw water pump 2 days ago and impeller still mint. Even went as far as changing the gauge. Drive in no.5 on indicators. Thanks, im really going nuts trying to figure this out. At begining of season had 35 psi at WOT, nothing has changed except new circ pump cause the other one was weaping. Is there different circ pumps? This one came from mercruiser dealer. Could there be restriction in circ pump??

could be, maybe your gauge is bad. But if your engine temp hasnt change it may not be something to worry about. This is just thinking out loud but if the water temp is much warmer like it has been out here this summer, maybe the water flows easier thus less presure.

I don't think the gauge is messed up, I thought that might be possible, so I changed it out and same results, I kinda doubt a mechanical gauge would be bad, but I tryed it anyway. A couple people have said to "just run it" but it seems that something is not right.

pressure is developed when there is resistance to flow... if no resistance, no pressure...
at 3k and under, your pumps flow enough volume to maintain the system at 22 psi.... about that, you're not moving enough water for the rpm... that can either be pump cavitation or the flow under the hull is causing starvation at the pickup...
possible belt slippage at that high rpm and you not able to hear it?

Mine dose the same thing i have given up talked to a bunch of dealears and they said not to worry some have more than others i have noticed that I have more pressure with captains choise off with would make sence becuse water flows out the pipes easier as long as ur oil temp is 160 to 180 and ur water temp is around 170 i would not worry u should have a 160 thermostat iv tried taking my thermostat out and i have less pressure and it wont get up to temp. IS UR WATER PICKUPS on the very bottom front of the drive like mine? Im beginning to think that could have something to do with it but i dont no.

Yeah, water pickups same as yours. Here's the thing I can't understand..used to have 35 psi at WOT, as Reggie report said. Now I don't, that tells me something is wrong. Not trying to argue with anybody LOL I just don't get it

On the front of your thermostat housing you have
4 hoses that go to your exhaust manifold. The two
That come out just over the hose that comes from
Your water pump, pull them off and check to make
sure the check balls are not stuck open.

you might want to check the fitting for the drive water hose, you need to pull the feed hose for the rwp off of the transom fitting remove the 2 -7/16 head screws that attach the black plastic water outlet to the transom plate[behind motor] and inspect the water hose fitting have seen quite a few corrode close restricting water supply

Is the brass tee still used in '97?

Not sure, I know sometimes the white balls get stuck open, when your thermostat is closed these bypass the water to your exhast, if one was stuck it would reduce pressure to the motor. I will look thru my service manuals and post a pic later.