Too Much water Pressure
 

Any suggestions I am getting way too much water pressure in my port 502 mpi it will bury the 35 psi guage and actually make the seal in the circulation pump leak and occasionly blow off a hose. I thought there may be a exhaust manifold issue (restriction) new thermostats, the manifolds and risers are cool to touch I even took the little rubber caps off the front of the manifolds plenty of water and that does not drop the pressure either. I have even tried to close off(partway) the intake hose valve. Engine runs at 150 degrees, and the starbord moter will not get past 105.

You need one of these:

http://www.offshoreonly.com/forums/s...e+relief+valve

those will work but we built a much cleaner system for my old 1999 35 with the 502 mpi's. when it was done you didn't even know it was there until you got on plane and saw the water streaming out of the dumps. told people I had blowers after that....LOL......BZ

My '99 502's had the same problem, pegged WP at 3000rpm. Watch the large water pump hose swell up when running, you'll chit!
I spent all last spring screwing around with dumps, t-stat housing, you name it, I tried/experimented it. After getting no where and tired of screwing with it, I bite the big one and bought the merc relief valves. What a waste of time it was before buying them. Buy them and be done with it, go boating.

I did replace the spring in both on mine to lower the pressure a little more, to a max of 20 psi at WOT. The spring was only a couple $$. I didn't want to drill holes in the boat for dumps, so I welded hose bungs to the back side of the switching valves in my silent choice divertor valves for that clean look.

I used the Mercury relief valves last year and they work. The mechanic cut the springs to about 12 psi.

too much water pressure
 

Do you think the current bilge dumps could be teed off and a check valve installed upstream of the tee.

Or if I could dump them into the little rubber cap on the factory exhaust manifolds until I change them

Any pictures of you fix thanks Brian

Don't see why not, as long as the check valves don't stick open. Not the best choice tying into your bilge system though. I'd make the dumps the straight path and the bilge the tee'd path w/ check valves since the dumps will be flowing all the time. Straight line shot.

Not sure I'd do the exhaust risor thing. Might run into water flow routing issues, creating other problems with the water already flowing thru them.

??

just dump them over-board...BZ

wow I am getting hit at $320 per valve ouch

I had mine "ghettoed-up" last year...ran the dumps off the thermostat housing and zip-tied a piece of heater hose so it hung out the side air-vents! Then I routed it more permanently thru a pair of dumps that had been installed for the previous owner's superchargers thru the transom.

I ran across a few here last spring when I posted a 'wanted'.
Ratman had 1 then. I bought 2 of 3 that T/Motorsports had. Way less than that price.

$320? must have been another big price jump. And to think, just a couple yrs ago they were $100 new from Merc. Guess Merc realized they created a problem wtht high pressures( but won't admit it) and now they convienently have the fix at a nice price. :rolleyes:

even at $640, you'll be glad you finally got the presure under control. Trust me. Just watch your water pump hose swell when running. :)
BTW, I have a pt# for springs that will lower the pressure to an even more desirable number that are an exact replacement.

I paid over $600 for mine last year. Dump through the transom. They do work.

Me too....I love them.
I "re-sprung" them (if thats a word:)) with the lighter springs and get about 18-20psi @ WOT.

that's crazy, my whole system with install was only $450.00 or $500.00??? and it had an adjustment valve....gods bless merc.......BZ

US1 Fountain i installed the merc valves looks like they are set @ 30lbs . im looking for the replacement spring to lower psi to 20 . do you still have the part # and were to get them. thanks Brian

Your lucky day Brian, I'm almost never on here anymore. Read this thread. Bought my springs in stainless from mcmastercarr. Page 5

http://www.offshoreonly.com/forums/g...-valves-5.html

thanks for the info battled hi psi all summer cant wait to get passed it . Brian