Water pressure relief
 

Hello All,
I'm putting on a -0 IMCO Bravo lower with a freshwater cooled BBC. Is a water pressure relief needed with a freshwater cooled set-up required. If so, what would be recommended before the season starts. Thanks for any input.

Only way to know if one is needed is to have a water pressure gauge hooked up when running at speed.

It's always good peace of mind. Do you have an clue what pressures you are seeing now?

I have mine plumbed after the cooler:
Transom pickup -> raw water pump -> oil/power steering cooler -> pressure relief -> tstat housing

I'm using the hardin marine 1/2 NPT relief valve at approx 23psi: part # 128-5000

Are you using dash pressure gauge for adjustment?

I don't ever recall seeing 20+ psi on my dash gauge, so I don't think the relief valve has actually had a chance to work

The valve is stated 7-25psi, so I marked the adjustment knob, put the vice grips on it and found the bottom / top positions and estimated about 23psi. If I remember correctly I did about 1/2 turn from the max position

In my experience 1/2" doesnt bleed off much pressure.
I use at minimum 3/4"

Where do you have yours plumbed at? I had to replace one of my salty ones. It's right on my strainer which feeds my 3 stage pumps. Not sure if it was even put there for anything other than pressure spikes from my water pickups.

I put mine on the bellhousing , shortest run overboard.
Strainer is also a good location.

Which valve do you have? I am assume you are using standard 1-1/4" hose? Perhaps it worth going to 3/4

I put these at 30psi
They are a quality piece, some of the other ones I`ve used lock up.

https://www.mcmaster.com/8088K16/

I use -12AN overboard

The lines to my strainers are 1.5"

Need to know what you're making for PSI first.
Pros and Cons to everything- We run the Merc Racing relief valves plumbed after the coolers before the t stat or crossover. Strainer mounted (or anything before the raw pump) ones can suck air if they stick open on first start, fast track to a burnt impeller. On the raceboat we used to cover the through hull with shrinktape to help it not suck air when we craned in. Once the boat was on plane and running, it would blow through the tape and didnt matter. It was better than replacing an impeller right before the race. The Merc Racing ones solved all of that.
The Mercury ones use a 1in outlet hose.

Anyone have a link or pics of how these are plumbed in? I am running 30lb pressure on the gauges. Hoses are plumbed to side of block where the water drains are.

As the comment above stated, it's usually recommended to plumb the relief in between the cooler and the engine. You get the most cooling that way, plus the least amount of issues with things such as the strainer

I'm using a 1-1/4" coupler with a 3/4" bung for the relief valve. Same logic applies if using braided cooling lines, I'm not aware of any diagrams but I can scribble one up quick if it's easier to follow

The 3/8" water drains?

I can picture that, but where do you dump it over? Put a thru hull on the side of the hull or on the transom?

Curious your thoughts on what I should have mine adjusted to since they are strainer mounted. Thank you.

Yes
30 is fine as long as you have checked it to confirm

The valve is adjustable from 7-25 so 25 it is then. I think I set it less than 25 so thank you.

Strainer/ valve: Swirl-Away High Performance Sea Strainers - 1-1/4" NPT HO Competition Dual Strainer Basket Sea Strainer - 10" Tall - CP Performance

Valve: Water Pressure Relief Valve 3/4" NPT - Hardin Marine (hardin-marine.com)

I ended up putting mine next to the bilge pump thru-hull on the side by engine vents, anywhere would suffice though

That`s where I put mine , before it goes into motor, discharge on the side along with intercooler, bilge pumps, exhaust water .

https://cimg5.ibsrv.net/gimg/www.off...cff4ed690d.jpg
https://cimg2.ibsrv.net/gimg/www.off...35add741df.jpg