Hey all, fighting a gremlin in my 496HO.

She is running super high water pressure, and when idling, going slow, she will overheat. It also will build temperature and the pressure is off the charts on the garden hose. I don't have to flush through the drive. At idle it is running around 15psi (way too high) the pressure has gotten worse since I've done everything below. I am also thinking the high pressure is related to the overheat?

I have the Hardin upgraded sea water pumps, I just replaced the wear plates and impeller. I changed all the temperature senders and sensors, I installed the high flow thermostat from CP, I thought I may have had the Bravoitis issue so I changed that hose as well. I pulled the heat exchanger and cleaned, I pulled the power steering cooler and cleaned. I can't get to the oil cooler easily but thought I did a decent job of backflushing. Maybe this is my issue? But i don't know. I have the EMI thunder exhaust setup for the 496.

I am completely baffled with this any input is greatly appreciated. Thank you!

Check your oil cooler

Water builds pressure only if there is a restriction. The more restriction the more pressure, less get less pressure.

Its not Bravoits because that would cause less pressure.

Is motor thru hull or thru the prop?
If thru the prop, which drive and have you checked if the water shutters have broken off?

Where is the sensor located and assuming electric gauge?

High water pressure you have a restriction somewhere, When I get high water pressure its the steering cooler on back of engine

How do you hook it up to the hose? Do you have a fresh water fitting with a Tee into the system?

Steering coolers on 496 are straight thru, no tubes (at least all the ones I've seen).

Not saying this is the case, but there was a PS cooler posted here where it was almost closed off from assuming over pressurizing, and it was not leaking

Yes it has a fitting, tee some sort of Perko fitting/valve.

It is a pressure fed gauge that is fed from a tap right off the sea water pump. It is through hull exhaust.

I need a serial number please?