Pressure relief valve setting...?

[fogducker III]

I picked up an adjustable (50-175psi) pressure relief valve. I plan on installing it just after the coolers and before the cross-over, what should I set this little sucker at.....:confused:

Thanks, Jeremy

PS. Application is a rebuilt, slightly mod'ed 454Mag EFI with a Procharger running 5lbs boost......raw water cooling. Bravo 1 leg pickup to sea strainer, to raw water pump, through oil, steering and fuel coolers, then the valve and into the crossover. Plan is no thermostat so no bypass and there is a feed line from the crossover to the intercooler.....

[gcarter]

Jeremy, I think you'll find the low number is a bit too high. It's hard to keep all the hose joints tight at 50 PSI. You'll end up w/water in the bilge on every outing!!!
How do I know this???
I would encourage you to look for something in the 15#-35# range.

[BUIZILLA]

35#......

[mrfixxall]

you want to get one that goes way down,,you need to run less than 25psi through the inter cooler..you need this one http://eddiemarine.com/store/cart.php?m=product_detail&p=13373&c=238and you want to t it off after the sea pump and before the coolers or run that bs set up that procharger uses..

[fogducker III]

So I have the right valve, Watts, like in Fix's link but wrong adjustment scale.....:nilly:

Anybody have a 15-40psi valve that needs a 50-175psi....? Just bought this one off OSO so not really looking forward to forking out $100+ for a new one....:garfield:

I was under the impression the valve was T'd in AFTER the coolers and before the crossover? :confused: The coolers handle normal pump pressure when stock right??

[mrfixxall]

So I have the right valve, Watts, like in Fix's link but wrong adjustment scale.....:nilly:

Anybody have a 15-40psi valve that needs a 50-175psi....? Just bought this one off OSO so not really looking forward to forking out $100+ for a new one....:garfield:

I was under the impression the valve was T'd in AFTER the coolers and before the crossover? :confused: The coolers handle normal pump pressure when stock right??

the reason you plumb before the coolers is to get colder water to the inter cooler for colder air,,if your pushing *100 degree water through the inter cooler it will only keep the air going into the manifold that temp,,cooler is better..

didnt procharger send you a cross over with the holes in it for the inter cooler?

[bertsboat]

I was going to buy this but I hope I dont need it. Good luck. eBay item number 110614798977

[mrfixxall]

I was going to buy this but I hope I dont need it. Good luck. eBay item number 110614798977

i have the item saved,,i was hopeing to get both of them for 50 ea at the end og the auction,,thanx for posting:bonk:

all he has to do is put a weaker spring in his then set it according to his pressure gauge..

[bertsboat]

The auction says if you buy one you can have two. Better email him and make sure he has two if you need two.

[bertsboat]

And, if you really need them better buy them now that the cat is out of the bag. These guys have been known to buy it out from under if you know what I mean.

[fogducker III]

I was going to buy this but I hope I dont need it. Good luck. eBay item number 110614798977


Thanks for that, doesn't ship to Canada....:garfield::confused:

[fogducker III]

And, if you really need them better buy them now that the cat is out of the bag. These guys have been known to buy it out from under if you know what I mean.


There is no Buy it Now.....

[fogducker III]

the reason you plumb before the coolers is to get colder water to the inter cooler for colder air,,if your pushing *100 degree water through the inter cooler it will only keep the air going into the manifold that temp,,cooler is better..

didnt procharger send you a cross over with the holes in it for the inter cooler?


Maybe I am being an idiot here.....if you reduce/slow the water down before it goes through the coolers it picks up heat from cooling the hot oil and power steering fluid down and that warmer water goes to the intercooler via the crossover...? So higher pressure and more water through the coolers and THEN the relief valve made more sense to me...?????:confused:

The Procharger crossover has a fitting for water in on one side and a fitting for water out to the intercooler.

I am under the impression the relief valve is for reducing pressure to the intercooler as well as slowing flow through the engine to remove added heat built up by the extra heat developed by the Procharger....?

[mrfixxall]

call me..

[fogducker III]

i have the item saved,,i was hopeing to get both of them for 50 ea at the end og the auction,,thanx for posting:bonk:

all he has to do is put a weaker spring in his then set it according to his pressure gauge..

Great, now I need a water pressure gauge....:boggled::bonk::wink::)

[gcarter]

I think I reject the idea that reducing the pressure also reduces velocity. Water is incompressable (well, maybe 3% @ 3000 PSI) so, just because you dropped the pressure from about 70 PSI @ 70 MPH to 30+/- probably reduces velocity very little if any
Thinking along those lines, install the PRV just after the inlet inside the boat.

[gcarter]

You can get the same valve for less @ CP Performance.

http://www.cpperformance.com/c-121-pressure-relief-valves.aspx

I would bet you can find it for less since it's just an off the shelf industrial item, I think.

[fogducker III]

I think I reject the idea that reducing the pressure also reduces velocity. Water is incompressable (well, maybe 3% @ 3000 PSI) so, just because you dropped the pressure from about 70 PSI @ 70 MPH to 30+/- probably reduces velocity very little if any
Thinking along those lines, install the PRV just after the inlet inside the boat.


I understand what you are saying George but placing the valve BEFORE the raw water pump defeats the purpose doesn't it...?

[fogducker III]

You can get the same valve for less @ CP Performance.

http://www.cpperformance.com/c-121-pressure-relief-valves.aspx

I would bet you can find it for less since it's just an off the shelf industrial item, I think.


CP valves are 7-25psi and are basically Hardin Marine valves which are Watts' valves (50-175psi) with a new softer spring installed, I spoke to the guy at CP that helped "develop" the valve...

The Watts valve is about $30 off the shelf at most hardware stores.....IMO it is a scam by CP Performance, Hardin Marine and Eddie Marine to sell these for around $100.....three times the cost....and all because very few applications require an adjustable valve around the 20-40psi range....:nilly:

[gcarter]

I understand what you are saying George but placing the valve BEFORE the raw water pump defeats the purpose doesn't it...?

No, because the real pressure is built by your pick up, whatever kind it is.
It's essentially a pitot and there's a formula for it somewhere.
This pick up pressure is what causes the problem w/the plumbing.
If, after you assemble the boat, you find the raw water pump is causing a problem, add a second valve. Keeping this in mind, maybe reconsider the location of the components.
IMHO, the raw water pump is only useful at idle and low speed.
I think that if your T-stat is properly set up w/some bleed holes, you won't have pressure problems.
But I've been wrong before.

[gcarter]

Jeremy, thinking about this a bit more, my Minx had closed cooling, so all I was doing was feeding raw water to the strainer, two coolers, raw water pump, and HE.
I never installed a pressure gauge but I did buy one and I had problems of multiple leaks in the plumbing due to the fact that the clamps on the copper coolers wouldn't hold at the pressures generated at 60 MPH or so.
Carl had pressure problems in his 525 powered 22, he has a thread about it. He installed the Tee and PRV like the one we've been referring to just after the strainer (I think) and the problem went away.
My TR has the same 25 PSI PRV mounted after the strainer and oil cooler, but before the steering cooler, raw water pump, and HE.
I think you'll find this arrangement, or something similar, to be pretty normal in most boats.
http://www.donzi.net/forums/attachment.php?attachmentid=59509&stc=1&d=1288106821
In this picture, which isn't up to date, shows the location of the strainer on the Starboard bracket to the right of the gimbal, the oil cooler bolted to the top of the gimbal, the water pressure gauge pick up tube is installed into the oil cooler drain port (even though this picture doesn't show it), and the Tee and PRV is in the straight piece of vertical hose exiting the oil cooler. That's not where I want it, but there's not a lot of straight hose where it can be installed. In hydraulics, the pressure in a system is largely constant so it really doesn't make a huge impact where it's installed but there're still preferred places. I did read on another site that the gauge pickup should not be in the strainer as the reading will be too erratic.

[fogducker III]

I appreciate all the info and understand your thinking, thanks George. :yes:

[fogducker III]

You guys will like this one......that link to the bay item turns out to be the same guy from OSO that I bought the relief valve from....the one I got is clearly marked 50-175psi and I contacted him and he stated that it is the same valve Eddie Marine is selling for $109. I pointed out that the Eddie Marine ones are 15-40psi and he told me to ignore the writing on mine, they are the same......:bonk::nilly:

Will be interesting to see exactly what the one he has listed on Ebay is rated at....:confused:


Funny thing is, he started the Ebay ad with two available and as soon as I bought mine from OSO he now says he only has one available via Ebay...:eek:

[mrfixxall]

You guys will like this one......that link to the bay item turns out to be the same guy from OSO that I bought the relief valve from....the one I got is clearly marked 50-175psi and I contacted him and he stated that it is the same valve Eddie Marine is selling for $109. I pointed out that the Eddie Marine ones are 15-40psi and he told me to ignore the writing on mine, they are the same......:bonk::nilly:

Will be interesting to see exactly what the one he has listed on Ebay is rated at....:confused:


Funny thing is, he started the Ebay ad with two available and as soon as I bought mine from OSO he now says he only has one available via Ebay...:eek:


do you have a air compressor with a regulator?? adjust yours to 40 psi and c if it dlows open @ 40 psi..

[fogducker III]

do you have a air compressor with a regulator?? adjust yours to 40 psi and c if it dlows open @ 40 psi..

Good idea, I will have to jury rig a fitting for it but it will at least tell me if I am in the ball park....:wink:

Where would you suggest I install the water pressure gauge fitting?:confused:

[mrfixxall]

Good idea, I will have to jury rig a fitting for it but it will at least tell me if I am in the ball park....:wink:

Where would you suggest I install the water pressure gauge fitting?:confused:

in the engine,,either in the side of the block or the intake,,foe the intercooler,,before it goes into the intercooler and remember for the water inlet you fill the inter cooler from the bottom up..

[fogducker III]

Finally figured out the story on this pressure relief valve. This is in fact from Eddie Marine, it is a Watts valve that started it's life as a 50-175psi unit, Eddie Marine swap out the spring and gaskets/seals and make it 15-40psi.....this is an older unit and the original writing/markings stating 50-175psi were still there, which is what concerned me, Eddie Marine now remove the markings after they "alter" them.....not a bad gig buying a unit for $30, changing a spring out and charging $109.....:boggled:

So now I am ready to T in the relief valve and hook the sea strainer up, just finishing making the mounting bracket for it and I am good to go.....also got the thru-hull fittings in, bilge pump outlet, engine flush connection, pressure relief outlet and intercooler outlet......now to just get the damn engine in......:nilly:

[Carl C]

Sounds like you got it sorted out. 25 psi is good if raw water cooled. Closed cooling likes closer to 40-45 on raw water inlet. Valve, dump and strainer definitely go before the raw water pump. I ended up taking the relief valve off of mine.

[gcarter]

I think Carl's point is interesting as he's using the low water pickup in his drive and generating 40 PSI +/- @ 80 MPH +/-, and I use a SM transom pickup in the transom.
I think the transom pick up produces a lot more water flow and pressure as the route is MUCH shorter and it's larger @ 1' pipe. While I never installed the pressure gauge in the Minx, at 60 + MPH, it was generating leaks in the many joints in the system.

[MOP]

I have done over a years research on this, flow in the system increases when the valve opens. For the reason most agree with putting the relief valve after your engines coolers is best, that gives you the added flow where you need it at higher speeds. There is an Active Thunder with a blown 540, he runs hos water from the pickup to the strainer then to his chiller from the chiller to the pump his valve is right after his oil cooler. Earlier he had the valve right after the strainer, he said moving it to after the oil cooler dropped his oil temp from 285 to 260. When the valve opens flow is increased before the valve and reduced after the valve as much of the water is dumped.

[gcarter]

That's an interesting point Phil.
I'm going to think about that some more.
It makes sense in a way.
But, I would think the valve needs to be in front of the pump as these positive displacement pumps can act as a valve also, i.e., they can act as a flow restricter as a transom pickup can supply more water at speed than the pump can use.
I may be able to get my valve inbetween the steering cooler and the pump.

[Fluffy Foo-Foo]

I don't know how they changed the spring in the Watt's unit. I tried with one and you destroy the valve. The adjustable knob is swedged into the valve body during the manufacturing process preventing its removal. There are no serviceable parts for these valves from Watts either (different pressure springs).:confused:

[fogducker III]

I don't know how they changed the spring in the Watt's unit. I tried with one and you destroy the valve. The adjustable knob is swedged into the valve body during the manufacturing process preventing its removal. There are no serviceable parts for these valves from Watts either (different pressure springs).:confused:

Check with Eddie Marine, Hardin Marine or CP Performance, they all do the same thing, not sure how, perhaps they will tell you. I do know the replacement springs are stainless steel...Once I get my system all hooked up I will be testing the PRV to see just how "acurate" it is.....:yes:

[MOP]

IMO the ideal setup would be water inlet to the strainer, oil cooler and if equipped the H/E then the relief valve. This would give the extra flow needed a high speeds but keep block pressure in line. Several of the folks that I have spoken with feel the 30psi Merc valve is still to much pressure, some with very high HP are only running 15-20psi with -0- issues. I have spent nearly two years reading everything I could find and speaking with quite few people, ever since I got some much extra pressure from the crank mounted pump. So far I have not made any changes as I am fresh water cooled, but if I were raw cooled I would have addressed it immediately knowing the damage it can cause.

[Fluffy Foo-Foo]

Check with Eddie Marine, Hardin Marine or CP Performance, they all do the same thing, not sure how, perhaps they will tell you. I do know the replacement springs are stainless steel...Once I get my system all hooked up I will be testing the PRV to see just how "acurate" it is.....:yes:

Maybe they are having Watts build low pressure valves just for them.

I believe if you order enough of anything somebody will build you what you want.:wink:

[fogducker III]

The question in my mind is, the stock "raw water" pump must push out pressurized water right? What is the pressure? My application is, stock Bravo 1 leg water pick up (holes on the side of the lower leg) so it is not like a low water pick-up nor a transom mounted pick-up which both would put out more water pressure, and even more at speed then the stock "side of the leg" pick-up, correct?

So that being said, some pressurized water is picked up and MUST be amplified by the raw water pump so I would think placing the pressure relief valve before the raw water pump would negate the point of the relief valve, are you with me so far?

The rubber impeller in the raw water pump must increase pressure as rpm's increase so a pressure relief valve mounted just before the block would make most sense to me...? After all, what are we trying to do is have constant water pressure correct? A safe steady flow of water protects the intercooler and keeps a constant, regulated flow of water through the block...??

The oil cooler, fuel cooler and power sterring fluid coolers don't care about what pressure is going through them, they are basically a tube with the encased fluid passing by that tube cooling the fluid......

So to summarize, I feel for my application, the set up I will try first is:

Stock Bravo 1 side of the leg water pick-up to the sea strainer, from the strainer to the raw water pump, water pump through the three coolers, then T'd to the relief valve (monitoring the pressure and heat) then into the crossover which feeds the block and intercooler, no by-pass and no thermostat......also, because of the cross-over, obviously no recirculating pump.

If this does not work I will obviously have to rethink it but as long as I carefully monitor it and make any needed changes, I can not see any harm coming from it......

Now to figure out the fuel issues.....:nilly::wink:


Thanks for all the input, Jeremy

[fogducker III]

Maybe they are having Watts build low pressure valves just for them.

I believe if you order enough of anything somebody will build you what you want.:wink:

I think that I mentioned that they are "modifying" their own....:wink:

That is the problem, there is not enough demand for a "marine" adjustable low pressure water relief valve......:garfield: Hence we pay $100+ for one......

[gcarter]

The question in my mind is, the stock "raw water" pump must push out pressurized water right? What is the pressure? My application is, stock Bravo 1 leg water pick up (holes on the side of the lower leg) so it is not like a low water pick-up nor a transom mounted pick-up which both would put out more water pressure, and even more at speed then the stock "side of the leg" pick-up, correct?

So that being said, some pressurized water is picked up and MUST be amplified by the raw water pump so I would think placing the pressure relief valve before the raw water pump would negate the point of the relief valve, are you with me so far?

The rubber impeller in the raw water pump must increase pressure as rpm's increase so a pressure relief valve mounted just before the block would make most sense to me...? After all, what are we trying to do is have constant water pressure correct? A safe steady flow of water protects the intercooler and keeps a constant, regulated flow of water through the block...??

The oil cooler, fuel cooler and power sterring fluid coolers don't care about what pressure is going through them, they are basically a tube with the encased fluid passing by that tube cooling the fluid......

So to summarize, I feel for my application, the set up I will try first is:

Stock Bravo 1 side of the leg water pick-up to the sea strainer, from the strainer to the raw water pump, water pump through the three coolers, then T'd to the relief valve (monitoring the pressure and heat) then into the crossover which feeds the block and intercooler, no by-pass and no thermostat......also, because of the cross-over, obviously no recirculating pump.

If this does not work I will obviously have to rethink it but as long as I carefully monitor it and make any needed changes, I can not see any harm coming from it......

Now to figure out the fuel issues.....:nilly::wink:


Thanks for all the input, Jeremy

Let me see if I can help....
Our raw water pumps are positive displacement pumps which means a set displacement exists per revolution, and no more water (or liquid) can pass through the pump than that design displacement. Also, water is incompressible. Keeping those two things in mind, only so much water can go through the impellor at any given moment no matter what pressure exists at the intake port. So, it's virtually impossible for there to be any difference in output pressure with different intake pressures. Centrifugal pumps are different.
If you want to change the pressure on the down stream side of the pump, simply reduce any backpressure, for instance, if you had a thermostat, drill some holes in it to reduce the pressure. Personally, I think it's a good idea to use a thermostat to better equalize temperatures in different parts of the engine. If no thermostat is installed (no restriction) the incoming water will find the path of least resistance through the engine and some parts of the engine will be hotter than what you want it to be.
In what seems like a former life, I designed marine diesel engine installations in ships of various types. All of them had closed cooling. All of them had to have a means of controlling the HE temperature other than the thermostat in the engine itself. What I did was to include a globe valve in the output side of the raw water plumbing. The globe valve allows very good control for throttling the raw water flow.

[fogducker III]

Let me see if I can help....
Our raw water pumps are positive displacement pumps which means a set displacement exists per revolution, and no more water (or liquid) can pass through the pump than that design displacement. Also, water is incompressible. Keeping those two things in mind, only so much water can go through the impellor at any given moment no matter what pressure exists at the intake port. So, it's virtually impossible for there to be any difference in output pressure with different intake pressures. Centrifugal pumps are different.
If you want to change the pressure on the down stream side of the pump, simply reduce any backpressure, for instance, if you had a thermostat, drill some holes in it to reduce the pressure. Personally, I think it's a good idea to use a thermostat to better equalize temperatures in different parts of the engine. If no thermostat is installed (no restriction) the incoming water will find the path of least resistance through the engine and some parts of the engine will be hotter than what you want it to be.
In what seems like a former life, I designed marine diesel engine installations in ships of various types. All of them had closed cooling. All of them had to have a means of controlling the HE temperature other than the thermostat in the engine itself. What I did was to include a globe valve in the output side of the raw water plumbing. The globe valve allows very good control for throttling the raw water flow.

Good points George, what happens when the rpm's increase and the impeller spins faster? Is that not like a fan where the air speed increases? not questioning you, just asking......

I do not have a closed cooling system and have no plans on using one, lots of Salt Away....

I do agree to a point on the thermostat and that is something I might have to revisit but with the Procharger my cylinders will be running hotter then "stock" so I would think a good flow of well regulated cold water should suffice?

[gcarter]

Good points George, what happens when the rpm's increase and the impeller spins faster? Is that not like a fan where the air speed increases? not questioning you, just asking......

I do not have a closed cooling system and have no plans on using one, lots of Salt Away....

I do agree to a point on the thermostat and that is something I might have to revisit but with the Procharger my cylinders will be running hotter then "stock" so I would think a good flow of well regulated cold water should suffice?

Yes, more water is pumped and pressure goes up against any resistance in the system when the pump turns faster. If you're trying to push more water in than can come out of the engine, the pressure goes up. High pressure or low pressure in the engine itself makes no difference to the engine, only the volume of water per unit of time is important.
OTOH, you won't have a pressure problem w/o a thermostat because the engine is wide open.
I'm aware your engine is raw water cooled, the example I used only illustrates the need for control of the cooling water traveling through the engine.

[fogducker III]

Yes, more water is pumped and pressure goes up against any resistance in the system when the pump turns faster. If you're trying to push more water in than can come out of the engine, the pressure goes up. High pressure or low pressure in the engine itself makes no difference to the engine, only the volume of water per unit of time is important.
OTOH, you won't have a pressure problem w/o a thermostat because the engine is wide open.
I'm aware your engine is raw water cooled, the example I used only illustrates the need for control of the cooling water traveling through the engine.

Agree, and wouldn't control of the cooling water be handled by correct water pressure/flow?

I think what I am getting at is once the engine is complete and I install, I will run it with the ADJUSTABLE pressure relief valve installed just before the cross-over, anything before that doesn't care what pressure, flow, volume etc the water is.....but after that point is what matters, so if the motor runs too hot I can adjust the water pressure, too cold, same thing...?

Perhaps I am symplifying things ......:bonk:

[gcarter]

W/o a t-stat, you won't have any pressure problem.

[MOP]

W/o a t-stat, you won't have any pressure problem.

The Tstat has little to do with the pressure, just regulates flow within the block, the pressure is the water no being able to leave as fast as it tries to come in hence the pressure builds. The risers are the only exit!

[gcarter]

Jeremy, I agree that if you end up w/too high of a pressure on the engine side of the raw water pump, some means of reducing back pressure is needed and a PRV is a good method.