what would be excessive water press for a bbc.. wondering what gaskets will take.

Ideally, you would like to keep it below 25psi.

I would be worried if the pressure was over 30 at wot.when I changed drives on a boat one time the pressure was 30 and over.this was due to the fact that the drive had a low water pick-up.this had a ramming affect and bosted the psi.i had to add a relief valve to control the pressure.18-25 psi is what I see now.

Much over 25 is playing with fire with standard head gaskets. If you have MLS head gaskets, then they can take more. However, there is no reason to have that much water pressure. It isn't needed.
Eddie

Probably a dumb question but how do you control the pressure? I have a relief valve on mine, and my guess is that it's relieving all the time. I see 25 all the time on mine, just not sure what to do about it other than hope the relief valve never fails.

-2 imco with LWP

Thanks

You can either have a larger bypass installed or dump some water out of the rear of the intake, or where ever you can. I almost always run a dump from the rear of the intake. This not only dumps off excess water, but it also stop any steam pockets from forming in the rear of the intake and heads.

Where is your bypass installed?
Eddie

Good discussion as I think I might have a problem coming with switching to XR's.

Sorry these pics aren't great, mine is installed just aft of the seawater pump. Dumps off the back where I can't really see it, even with the go-pro. It's worked fine like this for quite some time, just seemed like an expensive potential gamble that the blow off valve keeps operating properly-

How big of a dump is needed? Is it just trial and error?

Another thought I had would be to install a smaller hose fitting say just before the sea strainer. What I mean is take the 1.25 inch hose down to 3/4(as an example) then back into the sea strainer. Reducing the flow should decrease the pressure down stream. Rite? Or is this a bad idea for some other reason I'm not thinking of