installed new exhaust manifolds (rev marine) water pressure went from 18 to 30 wot. if i remove 1 of the 1/2inch pipe plugs on each manifold and install some sort of adjustable valve with it dumping overboard would it lower the pressure to be safe.

The pressure rose because the exaust is restrictive. It would be best to try to find the restriction and remove it. Anyways, I have a single 1/2" dump valve and it works great on my app.

the restriction is in the riser, what type of valve did you use.

I'd call the manufacturer and ask them why the tail pipe is causing a restriction. It might be as easy as opening up the water dump hole into the tailpipe. If you have to go with a pressure relief valve Merc makes one. http://www.offshoreonly.com/forums/s...water+pressure

Wett Vett on the board has one also.
Dan

I agree it's the easiest way to control water pressure, and it can save your gaskets one day if for any reason there was a blockage that peaked the water pressure above 30 psi.

this happened after i installed the manifolds, they keep saying i must have did something wrong .yes i have thought about the merc valve but i want mine back to around 15-18p.s.i w.o.t.

Can you post some pictures of the install. Something is wrong if your pressure went up.
Dan