SoCal Jet Boats

Tech Talk => Engine Mechanical / Electrical => Topic started by: bonzai272 on August 31, 2022, 07:30:26 PM

Title: Water flow and pressure question, and how much water through wet headers?
Post by: bonzai272 on August 31, 2022, 07:30:26 PM

Hi all. Picked up new-to-me jet boat and have a couple quick questions.

It has a 455 Olds and the Hardin 4-port thermostat kit in it. With this kit, water bypasses the engine and dumps directly overboard until the thermostat opens, then it allows water to flow through obviously and the hot water coming out then dumps overboard. Previous owner had gate valve wide open. Should I still need to regulate water flow via the gate valve with this setup or leave it full open? Just dont want to over-pressurize the engine is all.

https://www.hardin-marine.com/p-80797-polished-stainless-thermostat-kit-for-455-olds.aspx

Next question, after the gate valve, there is a tee and another gate valve that controls water flow to the over-transom headers. Previous owner had that shut and ran the headers dry. I would like to run them wet. I believe I just crack that gate valve open very slightly, so as to only have a fine mist when above 1800 RPM, and pretty much dry below 1800 RPM. Sound about right?

Thank you!

Title: Re: Water flow and pressure question, and how much water through wet headers?
Post by: bluthndr on September 16, 2022, 04:16:20 AM

I have pretty much the same setup (Olds 455, Hardin/cpp pressure relief/bypass at the jet, wet OT headers, 4 port Hardin thermostat) but no gate valves.  Water pressure in the manifold is 5-10psi WOT.  Water feeds the headers through a Hardin tee with a pressure relief that comes off the rear of the manifold.  If anything the headers get a little too much water off idle all the time, so I plan to add a gate valve before the tee.  Other than that it works perfect.