Old Topic New User/CMI 525 water in oil
03-25-2018, 09:25 PM
#11
IF the headers have a leak between the header outer cooling passage and the inner exhaust passage then water will leak into the exhaust port(s) WHEN the motor is shutdown. From there it will pass by the rings and into the oil pan.
03-26-2018, 12:42 AM
#12
Charter Member # 55
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If the headers are original to the 2004 boat in your profile, then its a high probability that its the headers leaking.
Probably lucky you caught it. There have been a lot of catastrophic 525efi failures caused by bad headers.
Probably lucky you caught it. There have been a lot of catastrophic 525efi failures caused by bad headers.
03-26-2018, 10:26 AM
#13
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The headers are from an insurance set of engines I purchased with less then 100 hours on them, total hours now of about 120. If they are the issue, then that is fine. I just want to understand how to clearly diagnose that they are and not go down the road of "well, thought it was this then fixed it, and now...". When I pull, what should I look for to clearly point out, that's my issue? Appreciate all the input.
03-26-2018, 10:44 AM
#14
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Do a google search for CMI header leak.. click on images and you can see the mess on the runners - clearly evident.
Run time hours you stated not really applicable vs having a leaking/ not leaking header
Run time hours you stated not really applicable vs having a leaking/ not leaking header
03-26-2018, 11:45 AM
#15
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The best way to test the headers for leaks is to submerge them in a big tub of water and then pressurize them with air (about 30-40 psi) and look for bubbles. They need to be completely submerged so that the primaries are totally filled with water. If they're leaking, it will be very obvious. I have found the easiest way to do this is to block off the top jumper hose port and the distribution rail port with 1" rubber furniture caps and a hose clamp and then connect the air supply to the 3/4" female port on the end of the distribution rail. Submerge the header first and then gradually pressurize the header until you get to 35-40 psi. I say gradually, because if you have not secured those caps properly, you'll want to know before you get to 40 psi, because it will not be fun if you're in the wrong spot when one of those caps blows off. The most likely place for internal leaks will be in the collector, which for the 525 is the worst spot because the engine is VERY prone to reversion due to cam overlap.
03-26-2018, 01:41 PM
#16
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03-26-2018, 03:01 PM
#17
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At older CMI the outside tubes are welded to the flange from cylinder head.
Newer CMI are outsidetubes end 0,5-1 inch before the flange!
The old ones real often leaking!
Michael
Newer CMI are outsidetubes end 0,5-1 inch before the flange!
The old ones real often leaking!
Michael
04-13-2018, 09:10 PM
#18
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Solution
Ok, finally figured it out. So I pulled the CMI headers and everything looked fine. While I was there, went ahead and pulled the Oil Cooler. I then took CMI's that were installed on boat, an extra set I have, and the oil cooler to the Radiator shop and had them all pressure tested. Everything was good except the Extra Port side CMI, which had a pin hole on the outside weld. I then contacted my dealership mechanic and he began to scratch his head too. He said he would call his Mercury "Guru" and he did. Mercury guy says, "Is he missing an exhaust flapper?". The answer was yes. He said to tell me to put my boat back together and fix the flapper. Apparently the stock 525 cam, at idle, without flapper, along with valve overlap, creates negative pressure and thus reversion. I put everthing back together, filled with cheap oil and new filter, and ran it to about 140 degrees. Checked the oil and it was very milky, but the level did not increase, and was roughly where it was supposed to be. Spoke to mechanic again, who told me to fill again with new oil/filter, and go run it. Put Mercury 25-40, along with Mercury filter, and went to launch. Oil level was slightly above normal before running, and I figure that filter and cooler needed to be filled. Ran it to running temp, roughly 160, and checked the oil. NO WATER or MILKINESS! Level evened out to exactly where it was supposed to be. After being told that it was the cam/valve overlap, saw a great video (Which I tried to upload here and had to retype entire response) which showed a stock 525 sitting on a pallet, running at idle. Person had a napkin at the rear of the pipe, and it periodically gets sucked back into the pipe. I am now convinced and will check my flapper, along with oil, every time I go out. Will try and upload the video in a separate post so that I do not have to retype. Hope this helps someone.
Last edited by geaux; 04-13-2018 at 09:15 PM. Reason: Add video
