Also, it depends where you're measuring. Is this the raw water side at the sea pump or the closed cooling loop?

I'm pretty sure my gauges are hooked up to the raw water side (which is exactly where I'd want them) and they read around 15 psi near WOT I think.

John

where can I find a pressure release valve and how are they plumbed into the sys.

I got mine from Hardin Marine. My closed cooling system is different than what most of you raw water guys run. I have my dump valve installed right after the sea water pump.
Since the seawater pressure has no effect on engine water pressure, I run it to 28 psi before it dumps.

I bought mine from Mercury. A nice item but really pricey. I've talked to others that have purchased other brands at a fraction of the cost.

Where are you guys measuring your water pressure at, sea strainer, intake manifold or block?

I am measuring off the block.