What is too low for water pressure?
 

I had a brain fart at the end of last year and started the motor with the hose turned off and overheated my impeller. Engine did not get hot before I realized it, but impeller was a little "fuzzy" and pump body was scored. I had a new Merc pump body, but the only impeller I had was an aftermarket impeller, so I went ahead and installed it. When I fired it up on the lake it was barely registering 1 PSI on the gauge, and was only showing 5-7 PSI when cruising. I never ran it above 3500 RPM last weekend, so I don't know if it would get any higher. Engine temps stayed steady at around 150*, oil temps were 180*-190*, and I was getting plenty of water out of my exhaust. Do I have a problem?

I ran this same type of impeller for years in my old 454 with no issues, but I did not have a water pressure gauge as a point of reference. Did a search on the forums for water pressure, but most were talking about either too high (30+) or no water pressure. Did not see anyone saying what the "normal" range should be.

There really is no "normal" psi range at idle.....as long as you have water flow going through the engine and your not overheating the motor then you are ok....psi is basically a measurement of restriction....you could be flowing TONS of water.... but with nothing restricting it you will have 0psi on the gauge

Not sure what textbook is. I know that my water psi gauge reads 0 at idle, about 12psi at 3000RPM, and around 18psi wide open. Engines never move off 100 degree water temp. (no thermostats).

I show 0 at idle. If I blip the throttle in neutral the gauges barely move. Cruising and WOT I'm around 7psi on the gauges. Scared me at first but my temps barely even register to the first line before 140. I'm runing crossovers without thermostats and dumping water from the rear of the intakes.

Hmmm sounds like I might be OK then. I'll keep an eye on my temps and watch the water flow out the exhaust. Thanks!