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"