525 water pressure problem
 

The start of a new boating season hey hey.......Thought I had my problem fixed but no such luck. Running a 2005 525 and I'm having a water pressure problem. At 4500rpm gauge is showing 50 lbs of pressure. The faster I go the higher the pressure. Back flushed the motor last fall after sucking the impeller. At idol its about 8 lbs. I'm thinking I could blow the water hoses off and cause some serious problem. Need some advise/help......thanks 815 236 3086

That is definitely too high and is probably indicative of an obstruction. Did your impeller disintegrate? If so, it's highly probable that you still have some pieces of impeller stuck somewhere. You need to completely flush all of the coolers and the heat exchanger individually.

Thanks for the advise. I did back flush the engine twice last fall and did get a lot of impeller parts. I just made a special tool to flush the engine again added an air valve along with the water valve. I'm going to give that a try. Do you know where the water pressure valve is located on a 2005 525 thanks again

The 525 efi has the water pressure sender in the oil cooler. Its an electric sender, if you have had a impeller blow, it would be on the starbord side of the cooler right where the pressure sender is. You need to make sure there is no pieces in there. 8 psi at idle is high, sounds like there is something in there.

Water Pressure Sensor in the oil cooler Mercruiser specs are bare min 20 psi - 60 psi MAXED at 5200.alsoi

Also it could be the sensor itself needing to be cleaned or replaced. Over time they can collect whatever deposits on them.

Thanks for the info....Im going to change the sensor and recheck the cooler again. Since I'll be in there I'm going to back flush the system for the 3rd time Called mercury racing tech. Told me 40 lbs wot was the correct number for a 525 blue motor.....also advised me to take it to a auth mercury dealer. I'll post the results. You are correct the water pressure sensor is located on the rear cooler on the left side.

This is where I'm at. Made a back flushing tool out of SCH40 PVC 3/4 " to 1" with a water inlet and compressed air inlet with valves. Worked really well. Removed both end caps on the rear oil cooler and blew out the cooler with air. Then back flushed to the fuel cooler with water and blasting shots of air. Then flushed from the inlet front cooler to the outlet of the sea pump. catching all the rubber parts in my wife's panty hose. Yes her panty hose and no she didn't have them on. Attaching to the end of the hose worked great. Recovered a lot of old impeller parts. This is the 3rd back flush removing lots of rubber each time. Just for information the impeller rubber doesn't float. I think what was going on was the oil cooler where the pressure sensor is located would get clogged up while running Turning off the motor most of the rubber parts would sink down the hose until the motor ran again clogging the inlet of the oil cooler. It's impossible to remove the oil cooler hoses without removing the exhaust rubbers due to the factory clamp install 7mm. I'll be running the boat soon and will report in.

still have the problem...I just pulled the port exhaust header section to rod out the oil cooler(oil cooler was clear) also back flushed all coolers installed a mech water gauge inline at the front heat exchanger ordered a new pressure gauge and sender blew out gauge water supply line will test after installing the gauge and sender will report after install

I have the same thing going on so Im dying to see what you find. I disintegrated an impeller last fall before storage so this spring cleaned everything out. I found a lot of pieces in the hose going up to the starboard side of the oil cooler and at that side of the cooler. I took all my hoses off and the ends off of both coolers, flushed everything put it back together and ran it last week. I didn't look at that pressure sensor so I'll have to take a look at that. Same as yours 8psi at idle and 50ish at wot. Unfortunately I have no idea what my pressures were before the impeller blew, I only drove it once after buying and before storage.

Well things are not getting better, Replaced the water pressure sender(135.00) replaced the water pressure gauge(100.00) in the dash blew out the line. Took the boat out today at 4500rpm's blew off the hose at the inlet of the front heat exchanger. Nobody seems to know what is causing the high pressure nor do they care. It's a strange problem but I'll figure it out. Mercury racing tech's are zero help. Didn't even know how the oil cooler was built. Advised me to contact a local mercury service tech. Note: livorsi water pressure gauge was redesigned 4 years ago from a spring system to a gear drive gauge Also, the water pressure sensor that I replaced only tells the computer if you have LOW water pressure which will give an alarm. While under the dash installing the new water pressure gauge I decided to change the light blubs to LED blubs. Well the small gauges will accept the new LED blubs. The monster speedo and the tach will not accept the livorsi LED blubs. The new LED blubs are too thick expanding the socket making it too large to reinstall the socket into the gauge. Anyway now the GPS speedo is stuck at 30 mph More problems. I'll keep this post open until I fix my high water pressure problem and I will figure it out it's only a boat engine with 94hrs

Im hitting the ole Mississippi tomorrow night, before I go I'm gonna flush things again, check that pressure sensor and just pray my hoses don't blow off. This is a weird problem, if all goes ok Ill make it home tomorrow night and post if anything changed.

Any exhaust side water flow restrictions ?

Well I placed a mech gauge( 100lbs) on the imput to the front(engine) heat exchanger and another on both the port and star inlet to the headers. At 3500rpm the heat exchanger gauge shows 35lbs the inlet header gauges show 17lbs each. Called CMI (Dave) again and discussed my situation. Dave is really a nice guy. He want my boat fixed as much as I do. CMI is willing to flow/pressure test my headers. I live about 3 hrs from their location in Wis. It would be a one day ordeal. Called Mercury racing again. Nothing new on that end. Chris the main guy is out on a medical leave. Won't be back til end of July. I'm not sure where to look now. Having 35lbs at the heat exchanger wants to tell me the headers. flushed the headers removing the two tail(Rail) input lines and plugs being the blue drain plug and the 9/16 end allen cap. Back flushed from the restrictors. Found nothing. ............... crazy crazy crazy I'm surprised with over 500 hits on this offshore only site and nobody has had this problem/answer...Like I've said prior it's only a 525 Mercury Blue Motor I'll figure it out. The bad thing is the Wife isn't very happy. I'll keep this post open River Rat

My 525s run 50 psi wot and have been since I owned the boat 4 yrs now. Never any problems

^^^^^^^^ Dave I know you bought the OEM Mercruiser HP 525 service manuals currently can you verify for me and whomever the water pressure specs and were it is taken. Please read post # 5 in this thread and see if I am correct as to what I posted. Thank you.. I sold my hp 525 service manuals a year or 2 ago.. Thanks again

Have a friend with a couple 525 efi's that consistently run over 40 # 's of pressure .No issues .The cmi headers have restrictors between header and tails that according to cmi help prevent hot spots in header

Yup I have both Merc manuals and in the diagnostic manual they state minimum 20 psi at WOT

I've been in contact with CMI regarding my high water pressure problem. The folks at CMI have been very helpful and are willing to do what ever to correct my problem. Yesterday I removed the restrictors and ran the boat WOT. I have about 45-47LBS pressure. Better water pressure without the restrictors. Still too high. My goal is 30-35LBS at WOT (Which is still HIGH). I'm going to run the boat for the summer as is. This fall the CMI headers are coming off and taken to the CMI factory for a flow test and a leak test. I'll keep this thread open until we test the headers this fall. Thank You all for the comments/concern. Problem still not fixed

RIVER RAT...............If you want to call me regarding our situation this is my cell number 815 236 3086

a friend of mine had this problem last summer, he finally removed both the engine cooler,, and oil cooler and used small wire to rod both, he got a 1/2 cup full of sand and some very small rubber impeller pieces out, he had back flushed a dozen times but flushing would not remove the pieces stuck in the tubes, they were stuck so tight he had to work to get them out but it fixed his problem immediately , good luck

thanks for the info when your friend had the high water pressure problem how high was it....

If you thread your gauge into the intake cts port or anywhere that reads whats in the block and hit a genuine 40 thats freeze plug poppin intake gasket seal compromising criculating pump seeping kind of pressure there. Not always, but likely . ,
see what cmi requires for rough gpm flow per header to keep them healthy your engine or exchanger may be generating more heated water that the cmis need or want

Maybe I'm missing something but the raw water pressure doesn't apply to the freeze plugs, etc. as noted. Certainly the various heat exchangers experience that pressure but the block is part of the closed system which is regulated by the cap on the overflow tank. BUP jump in here

(following comments are for water/cooling references only) Just looked at the Merc diagnostics manual and the only alarms or Guardian Activated situations occur for Low Seawater Pressure BLK PSI LO which will sound alarm and go to Guardian mode, coolant over temp ECT OVRHT also, block pressure sensor failure will give beeps but not go Guardian and coolant temp sensor failure will give beeps but no Guardian. I don't see any capability for the computer to indicate excessive raw water pressure and go to Guardian.

The block pressure is what would wake me up at night . If you have 50 at the pump outlet and its been good for years hey roll with it . If you have a exit problem ect and have 50 psi in the block its not all good .
if reads 40 wot at sensor that tells you if the pump is pumping 20 in the block 15 at inlet to headers and its not running hot then yea i wouldnt get freaked out about it

Doh ! Heat exchanger ! Prob big bad boy too . Removeable end caps i hope.
Now we are back to the guy at cmi ,and a poppet valve dump. Might get an extra 30hp you didnt know you had

The 50 psi is in the raw water side (heat exchangers, headers, not in the block)

I think this is the best route to take to try to solve this. It's not very likely that there is a restriction in the headers but you can try blowing them out with compressed air at about 70 psi. Good chance the heat exchanger is the culprit for an obstruction.

Another boating season.....Still have my high water pressure problem. My 525 is in the shop having valve springs and head gaskets. I now have 200hrs on the engine. Pulled the headers today and I'm off to CMI in the morning, David Rank at CMI seems to be very interested in my high water problem. We will be testing the headers and tail pipes for flow and pressure. I will post our results. Thanks for everyone's interest

i still think you have small peices of rubber& some other junk stuck in one of the coolers.as already stated,they need to be taken off the engine and rodded out.i had one in the shop a few months ago ,it had been backflushed several times before it came to me.i could not believe how clogged the cooler was.

A customer had high water pressure problem with a set of 502 mag mpi's with CMI etops, blew a couple hoses, and had high pressure at idle. I ran some tests and determined it was the tails. For a quick fix i cut the jumper port off the tail, dented in the inner pipe as the clearance can be really tight there on cmi's, then welded the jumper port back on. That completely fixed the one side, the other was still on the high side, ended up putting a new set of cmi's on that side and pressure was down where it should be. in this situation it was showing 5+ psi in neutral at idle, and of you revved it the pressure would jump upwards of 15 psi. What I did to isolate the headers the tails was pick up 6ft of clear 1" water hose. First I ran it right off the Tstat housing and dumped right over board taking the headers and tails out of play completely, only let it run for a few seconds, started it, revved it, shut it down. next I used the clear hose from the header jumper port and dumped over board to just take the tails out of the equation. Those 2 tests showed normal water pressure. Hooked the tails back in and water pressure was high again. Took no time to do

headers cmi
 

Just returned from CMI. Both headers were tested for flow and pressure. I have 22GPM water flow @ 20 lbs pressure on both headers. Pressure test was fine on both headers no leaks/cracks 40LBS pressure. The folks at CMI were extremely helpful and concerned regarding my high water pressure problem. A special Thank You to(sales engineer) David Rank. What a nice person. I was also very impressed with the factory and the CMI employee's I came in contact with during the testing process. What a great team.

I'll post again when I get the heads back on.

Has this problem been resolved. I suddenly have high pressure in a motor (carbed hp500). Gauge reads 25psi or over when I get up to 3500 0r 3800 rpms and will keep going up if I accelerate. So for now its lower speeds until its fixed.

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If you have the motor apart for a rebuild, take the heat exchanger apart and the oil cooler off and look through them. Sounds like this is the only option you have left. It is pretty simple and you would not believe the rocks, sand, and past impellors that will be stuck in there. A coat hanger and some compressed air is all you will need.

Just for the record the maximum water pressure on a 525 is 43 psi according to the Mercury shop manual. I often see over that due to the huge inlet on the Imco lower. I've had the inlet welded up some to keep it down. I know people who regularly run 50 psi on these engines and mine will get that high if trimmed down at speed. I can use my water pressure gauge as a trim gauge. I put in a pressure relief valve and dump but took it off when Allan Brown advised me to. After several mods to the water inlet I've got the pressure where I'm happy with it. I also did not do the header water by-pass elimination because my headers never get hot so I decided it's best to not restrict flow there if I don't need to. The proper water restricters are in the header water ports.

I pulled out the power steering cooler. Big chunk of fabric lodged in there so Ill see what happens later on the water. Oil cooler on the back and I'm not sure it can be pulled without pulling the motor. Whats the reason for not using a relief valve?

Sounds like you found the problem. When Brownie comes on here and gives me advice I take it and run! He said the relief valves can stick open at the worst time and the result can be disastrous. I'll try to find the post.

Still doing it. As soon as I hit 4000 rpm the water pressure jumps up quick. The PS cooler is after the oil cooler so maybe there is some of the same stuff in there. It wont be easy pulling the oil cooler though.

My water pressure is 15lbs @ 3400 rpms and goes over 20 - 25 lbs @ 5000 rpms. Last year my water pressure on one engine was at 10 lbs and the oil temps were on the higher side of 230 @ 3400 rpms. My oil cooler located at the back of the motor fortunately has removable ends caps. After looking inside there was sand, tiny rocks clogging some of the holes in the cooler. I used a small steel rod first and then back flushed the cooler. This corrected my water pressure and oil temp problem. From my seawater pump water flows to my combo oil/steering cooler first and then to my thermostat housing. My water pressure sensor is just a brass fitting on the right side of the block where water travels up a hose to my dashboard and connects to my Gaffrig gauge. It is a mechanical gauge. After reading all these previous posts
I am a bit confused as most of them said that pieces of the bad impeller clogged the cooler and is causing the excessive water pressure.. The way I see it is if the pieces of impellers, sand, rocks were clogging the oil cooler that would cause a drop in water pressure like a restriction, not an increase unless your water pressure sensor was mounted at the inlet of your oil cooler
My 2 cents