Also, where is the pressure sensor normally located?

better pic

not sure if you got my pm but im having the same problem with too much pressure. even with the overboard dump system I still have greater than 35 psi at 100mph. at 75mph the dump system looks like a water hose on high, think its 7/8in, but it still cant keep up. I have an imco sc lower lwp on my htm and going to try a reducer on the intake side of sea pump tomorrow. its a machined piece of aluminum that slides into the intake of sea pump. it has a small flange to not go to far into pump and reduces the about 1 inch hole on pump to about 1/2 inch. hopefully this will allow my dump system to be able to keep up with the excess water. even with the smallest crank and largest sea pump pulleys I had 7 psi idleing and around 35 at 90mph and about 37-38 at 102mph. gauge pegs at 35psi. like I said blow off was working but looked to be maxed out at top speed shooting a 7/8 stream past the outdrive at 75mph. I couldn't find a buddy to look at 100mph I think it will fix the problem, easier than welding up the intake on lower unit. ill be back! send me your email if you want some pics of the reducer. I have hell posting pics on here.

here lately my forehead but for the motor, mines on the front top where the thermostat would normally be. on the housing that sends water to each side of exhaust.

posting reducer pic for la/stryker

How about just a dump instead of a relief valve?

I put a restrictor in the in let of the water pump today. I'll see if it takes care of my pressure problem tomorrow. If it doesn't I am going to add a .375 dump out of my exhaust manifolds. I used a 3/4" pipe to 3/8" pipe bushing.

Id be cautious about limiting my flow into the pump, it may take the pump longer to prime. Aka, eat impellers faster.

I believe chocking the supply hose down will increase the pressure and decrease the volume. Not a good idea in my mind.

The orifice is about equal to an XR lower.

As far as increasing the pressure? Physically impossible. However, the velocity can increase through a smaller orifice.