Cap'm Kurt

US Fountain
I checked the McMaster Carr spring and specs showed it to be 0.080 thick wire diam at 13.30 lb/inch spring load rate.

I dont have the spring out of the Mercury regulator but if i recall correctly, the stock 30psi spring may have been smaller diameter. If so, this 080 diam spring would be even higher pressure than stock. I dont know the spring load rate on the stock spring, but it is MC part # 24-863728.

Just wanted to check with you to see if you were sure this one is lower pressure before i ordered it. thanks again.

US1 Fountain

iTrader: (1)

Can't comment on the spring wire dia of either with any certainty. Been a long time (years) ago. Pretty sure that I ordered those because they were the same OD and in SS, but a smaller wire dia, which was what I was looking for. Only thing I can say is it worked for me. If I recall, I cut 1 coil off less than stock free length off the new spring to lower pressure even more. Whether I used that one or put in an uncut spring as final use, I forget. I believe they come in a 4-6 pack so you can experiment. Start with it as delivered and go from there.

Cap'm Kurt

I will try them fountain.
I can see that both heads on both motors have been sipping a bit(salt water) over the last year right in the middle of the head on exhaust side between the two middle spark plugs. I put one motor together so i know it was done correctly. That is why i started reading OSO to see what people were doing about the water pressure. I saw a couple places where it was stated that even though Merc says 20-30psi, if you do have 30psi, you are going to see seepage at the head gaskets. I'm going to shoot for getting it to 20psi.

I know someone has very slightly ground off a several thousands off the OD of the spring to reduce the diameter to make springs softer, but it wasn't for this application. I will try that also if needed.

SB

iTrader: (1)

You want the bypass reg installed after all coolers and before the engine itself. This will give the cooler(s) full water volume for max cooling and the psi to be reduced/controlled for the engine.

US1 Fountain

iTrader: (1)

Yep


For Capt. I see I ran with the springs as supplied. Jumped in at post 36
http://www.offshoreonly.com/forums/g...-valves-6.html

Fordtrucks

You could shim your current spring with washers to increase pressure. You could heat up your spring with a torch to soften it for lower pressure, or possibly cut it down a bit. You could also install an adjustable valve. I use one from tractor supply that was adjustable from 0-250 psi. Then I cruised over to the isle with the assorted springs and picked out a similar sized spring that was only good for about 30 psi instead of 250... Adjusted it from there. I do not run a thermostat or circulating pump so my pressure gauge feed line is in my thermostat housing and my valve is in line between my sea pump and block inlet, dumped overboard.

minxguy

If you cut a coil spring the spring rate becomes stiffer, just saying.

Ken

Fordtrucks

I was thinking that shortening it would put less pre load on the valve, thus allowing it to open sooner.. Either way, get yourself an adjustable valve. I'm not familiar with the particular mercruiser valve, but beings I'm running a water crossover setup with no circ pump and no thermostat, I have spent more hours than I care to re count on dialing in my water pressure.

genob

http://teaguecustommarine.com/em0011...ief-valve.html

Cap'm Kurt

JUST OFFERING SOME INFO ON LOWERING THE 25PSI OEM SET PRESSURE FOR THE MERCURY PLASTIC 1.25" WATER PRESSURE RELIEF VALVES.
MERC # 863208A3
This PRV is located between the seawater pump and the oil cooler, which is the inlet side of the thermo housing.

Hope this helps someone in the future.


READ THIS >>>> There was on old timer on OSO that i found after many hours of looking, and he made a statement.............
" If you ever run over 20 psi on a stock 502, you will probably have head gasket leaks".
I wasn't sure at the time but I am convinced now. I had minor leakage every time on both motors, both heads, at 35 or so psi. Had leaks on heads that I had reworked also and put on myself, all flat with less than 0.0015.. Small leaks, no real dripping off the motor that i noticed, but could see corrosion below each head on the outside, below the head gasket towards the center of the heads, down to the pan gasket. On both heads.
I have never before or since seen that statement again. Glad i spotted it.



Merc OEM spring for this PRV, is part # 863728,
wire diameter 0.080"
You could grind down the OD on your original OEM Mercury springs. But i would have a spare on hand in case you mess up. I messed up the first try.

McMaster carr has a similar sized spring part # 1986K18. but is much much cheaper.
0.077 to 0.080" wire diameter, similar to Mercury OEM diameter, so you still have to grind down the outside of the wire slightly.
SS spring, 2.0" length, 0.938" OD $12-$15 for pack of six from McMaster Carr



WHAT I DID TO LOWER THE DUMP PRESSRUE FROM 25psi to 10-15psi, WAS TO GRIND DOWN THE MCMASTER CARR SPRING ON THE OUTSIDE UNTIL THE WIRE DIAMETER WAS 0.068" ,.
To grind them, I just hand held the McMaster Carr springs and put VERY LIGHTLY on a big belt sander, and carefully, slowly, steady, and evenly, just rolled it around to grind off the OD some. It was trial and error on how much i needed to start with but hopefully you can use my info and not have to guess so much. I have never had one fail after grinding it. Dont let it overheat either. A little at a time.

In grinding the springs, i was shooting for 20psi on the block, instead of the max of 35psi(block pressure) that i currently had. And this 35 block pressure was even with the 25# Merc dump PRV's (installed between the sea pump and the oil cooler).

I ended up with 25psi on the block max at wot. It took only 10/11psi at the PRV to get the 25psi on the block. This was a bit less at the PRV than I thought it would take in order to keep block pressure at 25 or less. But the 10/11psi spring is what it took.
But hey, it worked. NO LEAKS. No overheating ever. Tons of water.. So i left those 10psi springs in and have never seen one fail.



I am mostly stock motors except exhaust and much higher timing and air filters.
Hope this helps.