Originally Posted by MILD THUNDER (Post 3296670)

I think the circulating pump might help regulate in psi in the block. You can have high water psi due to the speed of the boat, hull pickup design, etc. Or you can have high water psi from a restricted exhaust water flow, etc. Some boats have relief valves in the sea strainers, to help protect from psi spikes when re-entering the water. The high psi from this can POP hoses off the strainer, pickup, etc.

Most scenarios though is too high of psi in the block, which can blow headgaskets and or intake gaskets.

My thoughts on a lot of high water psi complaints, is from exhaust that restricts water flow. The merc sea pump design puts out A LOT of water. The more you restrict the flow, the more psi is going to build up. My water psi is about 20 psi wot. My exhaust water dumps are 3/4". I bet if I reduced the dumps to say 3/8", it would drastically increase water psi in my block.