I was curious if insted of changing all my plumbing on the backs of my intakes would it be acceptable to add a water psi relief to the 1-1/4 hose after my lube oil cooler and before the inlet on the crossover? Or am I looking at this from the wrong angle and I have to put the reliefs on the back of the intake? If I do have to put them on the intakes is it acceptable to plumb them into the tail dumps? I read one thread where someone mentioned a psi issue related to the h20 alreading coming out of the tails. Thanks.

Hardin Sells an Adaptor just for that purpose , Merc puts the relief valves in before the engine.

Yip, I know of their adaptor and relief valves. You right tho, I did look at a stock merc psi relief today and its before the motor.. hhmm.. Thanks for reminding me. Appreciate that.
Wonder where that dumps to?...

Anybody see any reason why I couldnt plumb the relief back into the sea strainer intake hose?

At high speed the sea stainer will have more pressure than the motor any relief should go overboard. Just keep in mind sometimes high water pressure can be an issue with restrictions on getting water out of the motor. So dumping or relieving water before the motor doesnt make much sense, just raise the water pick up if you can. ? how much water pressure do you have

That makes sense, I see what your saying. The pickups have been "tuned"/filed to about 1/4" below the hull as it stands, with the trailing edge deepest. Right now with 3/4" restrictors we're seeing 25psi-ish above 4000rpm. I also saw about the same last test with 3 x 3/16" drilled t-stats; not Robert Shaw type, std auto type. I have two drilled high flow stats showing up tomorrow and I have some smaller restrictors to test as well. The boat was set up very good for warm water by the previous owner who had his temps/psi in check but now up in the cold water of Maine I'm forced to make some changes.

Mine is plumbed between the oil cooler and crossover. Dumps out back on top of the drive



last boat was plumbed before the raw water pump and dumped over the side

I have the water off the back of the intake manifold plumbed to the front of the manifold with a CP-128-5002 relief valve installed after the oil cooler and before the crossover. Works great! I dump the relief water over board.

Thanks, it sounds like your talking about two different reliefs in the above statement, both methods I'm familiar with. Could you take a few pics to clarify?

I don't think that I am able to post pictures. It says may not post attachments.