Water pressure; Looking for the real answer!
 

Does anyone know the real answer to the water pressure issue?
Searching all of the previous post it seems that the desired water pressure is approximately 5 lbs at idle and 22 lbs at WOT.
So I’ve been banging my head against the wall to achieve this the best way with my ProCharger setup. You guys have been very helpful with suggesting ways to achieve this.

Now I’m confused………I read a post in the general discussion threads called “496 goodies”, and there is a statement that says:
"With all our systems, we stress water pressure, we even have a Mercury Racing bulletin that states the same, they want a minimum of 25lbs. and maximum of 35lbs. @ WOT on all of their engines no matter what"

What gives here????????????
Thanks in advance,
Dave

:confused: :confused:

water pressure
 

Nordic,

I would assume your problem is too much pressure?

From what I know, there are several ways to limit your water pressure.

I had to do it on a Cigarette once a long time ago. The thing was making tons of water pressure. All we did was put an extra bung in the Headder tailpipe, and ran a hose to a fitting which pumped the water out the side of the boat. It was actually kinda cool, cause you could tell if you had watter pumping by just looking out the side of the boat. Just make sure you put the bung on the top side of the tailpipe so that you don't have hot spots in the pipe.

Another way I have seen it done if you have too much pressure is to put a bleed off valve in the water pressure hose. Outerlimits does this. Its a pretty simple system, and you have total control over exactly what you want your water pressure to be. I didn't look at the boat to figure out exactly how they plumbed it, but is should be pretty easy. Maybe someone here on the board has an Outerlimits and can give some pointers.

Thanks for the reply Panther...
I don't have a problem yet though; just trying to avoid one when I change over.
I would just like to know what pressures we should all be trying to achieve. It seems like their is some very conflicting information on what appears to be a very important aspect of these high performance engines.
I figured this would have a lot of response with all of the previous posts thier have been on this subject :confused: :confused: :confused:

The general concensus on the board is 5 at idle and 22 MAX at WOT.
Mercury Racing is saying minimum 25 and 35 MAX at WOT???

Thanks,
Dave
:rolleyes:

You will have with the Procharger or any other intercooled system, a slightly lower pressure due to the water dump of the intercooler. This has not been a problem with any of my boats with PC's. There is no thermostat in a PC system so the water flows quite freely......never more temp than 130 degrees water temp. Plenty of pressure thru the exhaust, cooler, etc. All normal original Merc plumbing. Ask yourself this - If water pressure is so critical to be between 22-35#, why does Merc NOT install a pressure gauge?.... They are worried more about temperature than pressure....after all insufficient pressure leads to excess temp..... with the PC intercooler water dump installed in the drivers SIDE of the hull, you have a constant visual indicator of pressure.:)

I second what blown formula says. Only time I saw my temp up to 140 was after I restarted motor ater letting sitting for few minutes. Most time 100-105. Unless you know you have a jproblem of some sort I would not worry about it. Too many other things to worry about.

In an automotive system the pressure cap is 15lbs I think, So Why "Mercury Racing bulletin that states they want a minimum of 25lbs. and maximum of 35lbs. @ WOT on all of their engines no matter what." Only reason I would know why is to keep steam pockets from forming when running hard.

Really you want as much water pressure as possible to raise the boiling point and remove steam pockets, as Turbojack has mentioned. The problem is intake and head gaskets will leak if to much presure is applied. I think 18 to 22 psi is a good compromise, especially if the boat is fast and pressure spikes may occur. If you run 35 PSI and get a spike when re entering at 100 MPH there will be a good possibility of a leak occuring and milky oil. As far as low RPM running 5 PSI is plenty if the temps stay down.

Gary Grimes Atlanta, Ga 770-475-5272
 

My water flow system by Gary.

540 ci N/A
Thermostat ( 160* @ idle and 140* any other time)

Water pressure relief valve by Grimes (7 psi @ 1000 r's and 18 @ 5600 @ 85 mph) This has a 1" ID dump @ transom that dumps water on drive :cool: All hose from sea pump to motor including valve pluming is 1.25".

360 hrs. :D no problems

Inside tip: If you are running a crossover. More than likely you will have more water flowing into on head than the other. For cure call Gary:mad:
Just kidding. Take a gasket from the crossover and make a new gasket out of a thin sheet of stainless steel. Do not cut out the water inlet hole in the new gasket. Instead drill a .4375" hole. (7/16") Put this new plate on the cold head (put another crossover gasket behind). Get an IR gun and compare head temps between the two. Open up hole as needed to get heads equal.;)

Excellent question. I think Im running way too much pressure at WOT (30+) but have not come up with a way to bleed it.
I also havent been able to get a clear answer on were it should be. Dustin as I recall said to run it on the Higher side. I dont remember what the actual number he called for, hopefully he will catch this post.
Im running a littly modified 502mag NA.

Why am I thinking a gaffrig gauge only goes up to 30 ???

Here is a solution for high pressure.
 

I have installed this valve on numerous boats that were having high pressure problems and have had no problems getting them down to that 15 to 22 PSI range. It installs by putting the stainless tee into the main 11/4 water pressure line before or after the oil cooler and then running a 3/4" heater hose from the tee to the adjustable valve, and dump it overboard. I have a few of these and can sell some as pictured for $110.00 plus shipping. It is a good idea to run a sea strainer before the valve to keep contamination from plugging up the valve. If crap does get lodged in the valve it will shut off and water pressure will go up to where it was before the valve was installed. The valve would then need to be cleaned by back flowing water or air through it. I haven't seen this happen on any of the ones that are out there that we are trying. Here is a photo of the valve and the stainless tee.

Getting off topic for a second

WV - I like that 1 1/4 pipe with the takeoff. I was looking for something like that to install right after water pump so I can get the coldest water to my intercooler. I have used my IR heat gun & have found that the water temp increaseds 4-6 degrees before it gets to the intercooler going thru the fuel, motor oil, & PS coolers. Not sure how big a difference the 4 degree makes in total HP. but every little bit helps.


Now back to your regular topic!

Turbojack, that is a good use for that tee. You could also put it before the sea water pump or before the strainer and run the 1/2" line to a 5 psi check valve that dumps overboard and that will all but eliminate pressure spikes. The best part about getting rid fo spikes in this manner is that they are gone before they get to the pump and the motor never really "sees" the spike. I have a few extra fittings laying aroung and could part with them for $40.00 plus shipping. If anyone is interested send me a PM.:cool:

Hey WetteVette (and others),
I would be interested in one of your Ts but need to know what the small hose barb size is.
I’m thinking of using it for my ProCharger intercooler and I believe, without looking, that the barbs on the intercooler are ½”.
You seem to be up on all of this water pressure stuff so if you don’t mind, I have a question. (open for all!!)
I will check my water pressure when I’m up and running but I think I’m going to be OK with the intercooler plumbed in to the system along with a bypass.
My question is about the bypass.
Unlike most PC setups, I will be running a 120 thermostat because of my FAST ECM. I don’t have to, but I want to be able to utilize all the good things in the ECM such as cold enrichment and such. Our springtime water here is very cold!!
I’m going to run a 120’ thermostat and probably just drill one or two small 1/8 hole(s) in it for air pockets, etc… I will use your T or one like it right after the pump to go directly to the intercooler. I will then use the original intercooler fitting on the PC crossover for a bypass. Question is, can I run the bypass hose to another T and then to the fittings in the top of my CMIs that aren’t being used? I would think this would direct any cold water away from the thermostat and still feed the exhaust when the thermostat is closed. When the thermostat opens at 120’ the water should exit through the larger hoses from the thermostat housing to the main exhaust inlets.
Does this sound reasonable and has anyone setup any system like this?
Thanks
Dave

Hey Mike, 360 hours on that motor?
Thought these GenVI blocks couldn't take the punishment:D
I've got 130 now and it just seems to get stronger:D

At 125 hrs I put 100 more hp in the motor. Also new rings, valves, springs, & bearings.

My buddy's (OSO-LAKEJUNKE) PC:
Built 502. Removed fuel inj. & now carb.
Seapump, oil cooler, P.S. cooler, 1st tee 1.25 x 1.25 x .5?, 1.25 goes to 2nd tee & .5 goes to intercooler, 2nd tee 1.25 x 1.25 x.75?, 1.25 goes to motor & .75 goes to 3rd tee, 3rd tee .75 x 3, the 3rd tee feeds both headers.

He is running a stat w/ holes w/ no problems.

B4 this system he was running PC stock set-up & no water pressure problems @ 5000 rppm. Then his 3 yr old impeller:rolleyes: died. When he replaced impeller his pressure went from 17 to 25+ (25 was at 4000) He had some engine problems & did this summer & didn't get the chance to see what 5000 would have read. I don't know if he has had a chance to see what new sys. does at 5000+ r's.

NordicHeat, the tee shown in the picture has a 1/2" NPT half coupling on it and the fitting in it is 1/2"NPT thread to 3/4" hose barb. You can pun any fitting you want into the 1/2 NPT thread. As for your bypass are you talking about the water after it goes through the intercooler? Dumping into the headers would work and it will save you from having to drill holes in your transom for dumps. Does the water in the intercooler need to be pressureized? If so you can put a check valve or pressure relief at the outlet of the intercooler which will maintain a constant pressure. With a pressurized cooler there will be no water flow through the cooler until the motor water pressure exceeds the check or relief valve setting. Cool ideas!!

High pressure solved
 

My trip 540/500 bulldogs were running with the gauges pegged at 35 psi after I changed my raw water pick up pumps. Merc says that new pumps can increase water flow by as much as 10 to 30 %. Merc just came out with pressure releif valves. I installed them and now pressure is 15 to max 25 psi. Valves are $114. each direct from merc. People told me that with water pressure at 35 psi and over....it's just a matter of time before you go through a gasket.

Re: High pressure solved
 

Can you post a pic of the Merc Valves?

Last year I had to remove the thermostats (160*) from my engines because it caused too much water pressure. Try about 125lbs @ idle (in neutral) and if you bumped the throttles up to 1500rpm (in neutral) the pressure guage would show 135lbs! The engines were only running about 140* water temps WITHOUT the thermostats and 5-7lbs of water pressure constant---even at WOT. Because I have aluminum heads, I want to build a little more heat into them by being able to run the 160* thermostats. I have a water pressure relief valve (1/2") on each engine and it's not enough---still too high of water pressures. I have a ball valve on the raw water intake hose for each engine that are located just before the sea strainers. Perhaps if I close them a little bit and adjust them to the lower pressures I need it might help.

I also would like to see the new Merc water pressure relief valves.

Craig/Wette Vette, I may have to have you take a look at my set up---lots of plumbing! But then I think you eat up that kind of stuff! :)

I'll set you up with one of the valves I have been using for a good deal. 3/4" ports and I have a few left. Talk to ya later!

TTT

Ok...a stupid question....does drilling holes in the thermostat correct ANY of the high water pressure? My builder has told me that I am above 35 and I am getting milky oil. First question....do I need to have him change a gasket or will it be ok once I lower the pressure?

I'm thinking that the water dump into the exhaust would be an option.....what would I need to do this correctly?

Thanks!

Dave

Dave,
Holes drilled in your thermastat can not flow enough water to lower pressure more than a few pounds. Holes are mainly for when the stat is closed.
My thought has been that the holes are more to allow the block to fill by bleeding off the air while the stat is closed at start/warmup. And also helps put 'some' hot water on back side of stat. Also consider this, if you have high pressure, it is because your stat is still closed because motor is not up to temp. Sounds like you running a crossover and trying to use a t-stat??

Did you recheck your intake bolts? All my intake leaking experience has just been leaking past the gasket, not blowing them out. So just retightening the intake should be fine. Or at least the answer to your problem if it is the problem. Then you can decide if you want to install new ones. BadDog had this same problem this spring with his new motor. Tightened intake in many rotations, all is good now. Please check this.

Ok...next question.....after I check and re-torque the intake manifolds.....where is the water pressure sender? I don't currently have a water pressure gauge...is there a sender already or do I need to put one on? Where is the best place to put the sender?


So...who has these valves and how can I get one? (if you don't personally have one...a manufacturer and part number would help!!)

If I don't drill a hole in the back of the boat....it sounds like I can just dump the overflow into the exhaust....will it hurt anything to dump it just to one side or how would you recommend dumping evenly into the exhaust????

Thanks!!!!

Dave,
Pressure gage should be installed in the block. you can remove your drain plug and get a fitting with a hose barb connection instead. Any hardware will have it. Mercury makes a gage for the outboards that fits a 2 1/8 hole. If you try to dump too much water through the exhaust your exhaust will have to "fight" the water on the way out and performance will suffer. On some stock setups others have reduced the water to the exhaust for better flowing exhaust. Re read the other threads on water pressure and do a search on dump valves. Wette Vette has a rig all setup for you and has done the homework. I did my own and it took some dialing in.

Dave,
I installed a pressure relief valve last year after my rebuild as well as installing a water pressure guage. I removed a plug that was on the intake manifold, installed the sending unit and wired up to the guage at the dash. Works perfectly. Used Gaffig components. As far as the dump is concerned, I did drill a hole in the transom.

This may sound hokey, but if you are really concerned about drilling holes in you transom, another solution would be to dump through your existing bilge pump thru hull outlet. This could be accomlished by installing a tee before the outlet and reconnecting the bilge pump and and the pressure refief dump. However, to stop the relief water from being pumped back into your bilge area and vice versa, a check valve (sized the same diameter of the hose) would have to be installed on each line before the tee going to the thru hull fitting. These small check valves are readily available through Grainger or McMaster-Carr where I in fact purchased the pressure relief valve.

Hope this helps!
BTW, My pressure went from 35psi at WOT to 25psi. I can adjust the relief to any setting from 0-50psi.

Paul

Relief valves
 

Pb,
Which valves did you order from McMaster Carr or Grainger.Do you have a part number.
Also should the valves be located before or after the seawater pump.
Mark

TTT
 

Just wanted to bring this back up again as I am looking for Mercury Pressure relief valve part # as described in earlier posts.
New motor & my pressure is way high.
Thanks John

I've done quite a bit of testing on engines, Mercury Racing has done 10 times more. You need water pressure in open cooling systems to relieve steam. The back of the heads do not have a passage out, the water enters the front of the block, fills the block and heads, and then exits the front of the intake. The water in the back of the heads does not circulate and can become stagnet in the back. Steam can form without proper cooling. If steam forms, it will need psi to push it out.

Theres also a varaince depending on the use of a circ. pump or just the sea pump with a cross over. We do what you see in most racing applications, we bleed the back of the heads through the back water passage on the manifold. We bleed a 1/4" line right out the back of the boat through one -8 thru-hull dump. In the early stages, we installed clear hose just so we can watch the water and possible steam. You won't believe what you get out of there.

You don't truly need 25lbs of pressure, but because of the distribution of the water through the engine, the high X dimensions, the stepped bottoms, psi is very important. Some boats that have 15 will be fine, some that have even 5 will be fine, it depends on many varibles, but some of these pick up so much air, your psi reading is not accurate. You can see with clear hose the bubbles, steam, etc. coming out of the engine. So in most cases, Mercury Racing, Sterling, Pfaff, Eickert, Whipple, etc. all call for high block psi. This will eliminate some of the possible problems, will typically allow for higher spark advances or more boost, etc and overall, more reliability.

Water temp is not always a direct relation to water flow. Motors can run 90 degrees at 700hp and only have 5lbs of block pressure. Thats a huge potential problem.

Thanks,
Dustin

I am running 500HPs with Stainless Marine strainers with overpressure dump over drives. I put crossovers on motors. At WOT I get 7-10 psi water pressure from each moter. Idle shows no pressure. Water temp never gets past 105. Oil temp at WOT hits 260. When I put in new impeller, I hit more consistent 10psi. Should I check head temps etc. SHould I have thermostat or not?

My water dump system
 

:drool:

2
 

:drool:

3
 

:drool:

My procharged 502 runs at around 5 lbs Idle, and It can run at any pressure I set it for WOT. But I'm set at 24 psi.
I put my pressure relief in the procharger cross over.
My intercooler is fed by the outdrive when under way.(Thats why theres a red X on the picture). I have a 1 1/4" thru hull feeding the engine via sea strainer. My Stat housing dumps over board, Don't need the extra water steeling any HP.:D:D I run a 120° stat with 1/16" hole, because I boat in the N. East and engine water temps never see above 90° without a stat. I have been running this set up for 280+ procharged hrs. 40 of them this year.

Merc Water Relief Valve Pictures
 

Look in the general discussion thread. I posted a picture and sketch.

offshor, can you post the link to that thread??? Mine is set up like this except for the intercooler goes to a billet drive shower cap.
Also you don't have to relocate your oil cooler, Mine is there because I had to relocate for the super charger. The stock location is fine.

Post
 

It's on page 2 now of the "general discussion" section.

"merc water pressure releif valve picture "

Whats the name of the thread offshor??:):)

Merc
 

" merc water pressure releif valve picture "

Water Pressure
 

Wette Vette's deal works.......

I had two motors over 40 psi on water pressure. The system is fully adjustable for each motor. I comfortably run under 22 psi WOT.

Mike
Apache 28

Sorry Offshor, but a search using

" merc water pressure releif valve picture "


brings you back here.....Thats a search in all forums...

Here ya go...........Merc relief valves