Block water pressure

[HP350SC]

I found that Mercruiser makes a pressure relief valve for stern drives set at 30 lbs. They cost $103 at Bam marine. Have not found any pictures yet, was hoping someone had some. The part number is 863208a3. Anybody got pics. or use one of these?

[DogHouse]

I bought a valve from McMaster-Carr and put it inline before my oil cooler. I have it set at about 15 psi. These valves aren't cheap, so for once the Merc part is actually a decent deal.
-brian

[HP350SC]

I ordered one, will be here tomorrow. I'll post pics. if anyone is interested. I know you can get a valve at Graingers, but liked the idea of a Merc. piece.

[RACER52]

does everyone use these relief valves??? some people run without them and have no problems

[HP350SC]

Yeah, you will need to regulate your water pressure. Especially at your projected speed of 120mph. 25 lbs. is recommended. Spikes can be well in excess of 35 lbs. and it's bye-bye head gaskets. There is also a threaded metal fitting available to replace the plastic barb fitting at inside of transom. I know of one 100+ mph Cougar that blew the hose off and cooked the motor almost instantly (at least before driver knew what happened).

[HP350SC]

Here's a picture of the valve although I haven't hooked up the bypass hose yet. The directions show it mounted between the oil cooler and p/s cooler and pointing tthe way it's shown. Would be better if bypass pointed to the rear.

[RACER52]

hp350 or anyone else,
if the head gasket can take the boost i.e.(cometic)than why wouldnt it take the water pressure??
hulshot runs the copper gaskets without a relief valve??????
if i have to get one I need to order now
what plastic barb are you talkin about. Is it for water pick-up in the drive through the transom??
Racer

[Snowboat]

The water pressure can get much higher than boost. Before installing a bypass, and other plumbing mods, my block pressure headed towards 35 psi at 7,000.

[HP350SC]

Originally posted by RACER52
hp350 or anyone else,
if the head gasket can take the boost i.e.(cometic)than why wouldnt it take the water pressure??
hulshot runs the copper gaskets without a relief valve??????
if i have to get one I need to order now
what plastic barb are you talkin about. Is it for water pick-up in the drive through the transom??
Racer
The plastic fitting is on the inside of transom where your seawater pump hose connects. It has a 2 bolt flange mount. Hose slides on it and clamp to hold it. The better fitting is all metal and is threaded for AN fitting I believe. I don't have one yet, Cliff showed me one he bought. I will find out where to buy them.

[RACER52]

does anyone make a bypass that is fitted for an-lines??
and if you have the mongo oil cooler with the built in p.s. cooler would you put this after or before the cooler?

[HP350SC]

I would say after the cooler just to be safe. There probably is other threaded types of valves that will work, but the merc. one is relatively cheap and about as easy to install as it gets. CP sells a 1" stainless transom dump which is the size of the merc. bypass outlet, I ordered mine yesterday.