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Water pressure Mercury Racing 525 EFI

Old 07-05-2015, 10:55 AM
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Default Water pressure Mercury Racing 525 EFI

Two weeks ago we ran aground. Alarms, Guardian mode, etc. Temp went back to normal. Drove home slow, but water pressure higher than normal even at 3000RPM. Back flushed entire system, got good flow. Took it out yesterday, lower water pressure but still higher than normal, i.e. gauge was pegged, over 40lbs. Nailed it once, gauge buried, motor turned only 4800, usually 5450, then backed way off. I'm gonna put a sea strainer in it, but I'm worried motor is lame. Everything sounds good and still good flow. Any ideas why motor did not turn up? Thanks for help!
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Old 07-05-2015, 11:19 AM
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Did you change your impeller?
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Old 07-05-2015, 11:20 AM
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Mechanical gauge or electronic/SmartCraft? Did you pull out the water pressure sensor and clean it out specifically? They can get crud in them throwing off readings.
I am wondering if you are being limited on power by the ECM.
Have you scanned it to see what available power is?
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Old 07-05-2015, 11:44 AM
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Yea ,what he said . Should be able to start probing around witb a mechanical pressure gauge , hopefully you have some room. 40psi can get water in the oil , and the engine if you have a issue with heated water not being able to exit the engine and exhaust fast enough.
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Old 07-05-2015, 06:12 PM
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ECM is reading the high pressure off the water pressure sensor and the guardian is preventing the motor from turning higher. After a grounding, you should change the impeller, remove the water pressure sensor and clear it out, as well as the tube that leads up to the gauge assuming you have one. Also, back flush EVERYTHING.... remove the hoses and run water through all of the coolers, pull the drain plugs from the power steering and fuel coolers and flush them. Flush the heat exchanger.
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Old 07-05-2015, 07:22 PM
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100 % agree read what available power is from the scan.

bad sensor(s) / fault code(s) - the PCM can put the engine into a form of guardian mode offering engine available power at only 90 % to complete shut down and of course anywhere in between.

IMO I think you are running at 90 % available power as the PCM is limiting (10 % engine guardian = 90 % available power) Scan it and see what it shows..

I would replace the water pressure sensor regardless - they can be a problem anyways.
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Old 07-05-2015, 07:31 PM
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Originally Posted by BUP View Post
100 % agree read what available power is from the scan.

bad sensor(s) / fault code(s) - the PCM can put the engine into a form of guardian mode offering engine available power at only 90 % to complete shut down and of course anywhere in between.

IMO I think you are running at 90 % available power as the PCM is limiting (10 % engine guardian = 90 % available power) Scan it and see what it shows..

I would replace the water pressure sensor regardless - they can be a problem anyways.
Bup I'm always impressed with all info you have to offer. Thanks on behalf of all of us and if we ever meet the drinks are on me!!!
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Old 07-06-2015, 12:14 AM
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Thanks! You all were a great help! I really appreciate it.
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Old 07-06-2015, 05:53 AM
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Just FYI; Service manual says 43 psi is max raw water pressure. I often exceed that. I know someone who confided in me that he runs over 70 psi regularly on his 525s with no problems. He won't say that on here because he'll take a beating! It's closed cooling and likes higher pressures. I try to keep 35 minimum on hard runs. This does not explain why yours shot up though. I ran over a reef at Put-in-Bay and filled my cooling system with crushed shells. Had to get towed in. After back-flushing everything was fine though. I put on a sea strainer and never looked back! Good luck.
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