Merc water pressure issue...

[Vinnie]

My new water pressure gauge is acting nuts... At idle, it appears to be doing fine. Under accelleration, it goes up to about 15 lbs and then DROPS to about 7lbs on the gauge. The water pressure gauge is new, the gearcase had a new pump installed. Yes, a good stream is coming out of the "peehole"....

I did change the water pressure hose at the same time to a slightly large one..

Any idea why the pressure is dropping? Can there be a leak that only happens under pressure?

Thanks in advance..

[transomstand]

If it's a V-6, the poppet will open at about 1500-1800 rpm, will drop the pressure quite a bit, but 7 lbs is a little too low for me.

[Vinnie]

It's a 225 MoMax.. Note, I have only driven it for about 2 minutes.......

[CharlieB]

Vin it sounds like a poppet valve problem. It should open around 2000rpm to let more water flow. I bet the spring is weak.
If I remember right the hose was on top of the divider plate. Try moving the gauge line
to the output of the poppet valve. This way you can monitor it just for diagnosing the problem Ya may need a diff fitting. I have one here if ya need it That should tell you where the drop is