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  1. #1
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    Default Water in Cylinders - Bad Manifold?

    1989 OMC with Chevy 4.3 V6 - I have read many topics on the "water in cylinders" problem (which I have). I have also posted a few questions and received helpful responses. Many people suggest that bad exhaust manifolds and elbows could be the potential problem in addition to a blown head gasket. Can someone explain the theory behind how a bad exhaust manifold could leak water into the cylinders? My OMC manifolds are 1 piece meaning that the design combines the function of the manifold and elbow into 1 piece. Inside this part, I assume there are four passageways - 3 for the exhaust gases and 1 for the water. How could the water get into the gas passageways if they are seperate? Even if it did get in through a crack, wouldn't the pressure from the gases blow it out? In addition, some have called to question the exhaust manifold gasket. If this gasket just seals the gases, how could a problem with the exhaust manifold gasket ever lead to water in the cylinder? ...unless maybe condensation or water sprayed over the manifold...

  2. #2
    Commander Lou C's Avatar
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    Default Re: Water in Cylinders - Bad Manifold?

    The cast iron between the ex gas section and the water cooling passage can rust through, and when you shut off the motor the seawater can flow in thru an open exhaust valve. If you are in salt water they are way over due for replacement. I replaced my one piece OMC units the year a couple of years after I got the boat because I had no idea how long they were used in salt water. I was not having any problems and they still looked good but they were then 16 years old! This boat was from the midwest originally so most of the use was freshwater. I plan to take them off every 4 years and check the exhaust and water passages, when you start to see flaking rust it is time. Most say 4-5 years in salt is the limit. Those may not be available from Bombardier any longer, doug russell marine in Mass may have em, I got a spare pair from them last winter. There is a place in Washington State (Sea Way Marine) that sells a conversion kit so you can use the Merc V-6 manifolds and regular risers.
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  3. #3
    Admiral KaGee's Avatar
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    Default Re: Water in Cylinders - Bad Manifold?

    You have the "batwing" style manifolds. The manifold and the riser were built into one piece eliminating the riser gasket.Basically, you have an exhaust manifold that is surrounded by a water jacket. Water is pumped through the jackets cooling the exhaust manifold, making it safe to be enclosed in a boat setting.Water intrusion into a cylinder can be caused by a number of circumstances. An exhaust manifold with a rusted out water jacket is the most likely source. If yours are original, I would suspect that is where it's coming from, but you should troble shoot it first.Read THIS
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  4. #4
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    Default Re: Water in Cylinders - Bad Manifold?

    Thanks! My auto mechanic/friend told me that even if water inside the manifold leaked from the water jacket into the manifold, the pressure from the exhaust gas would blow it away from the engine and not let it back into the cylinders. Is this true? If not, why?Could water ever run through the exhaust manifold without the engine running? If so, there's the answer I guess...

  5. #5
    Supreme Mariner Haut Medoc's Avatar
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    Default Re: Water in Cylinders - Bad Manifold?

    That's the answer.....Esp ecially on any valve is on the intake or exhaust stroke....JK
    Disclaimer!: In my inexpert opinion......

  6. #6
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    Default Re: Water in Cylinders - Bad Manifold?

    Could water ever run through the exhaust manifold without the engine running? If so, there's the answer I guess...
    It's not so much as the water running thru the manifolds without the engine running,.........It's the water that's left Sitting Inside the manifold when the engine is turned Off,.........It runs thru the Cracks, Into the cylinders,.. Pass the Rings,+ Into the oil pan,.........
    Any Grease is Better,..... Than No Grease at All.......

  7. #7
    Admiral KaGee's Avatar
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    Default Re: Water in Cylinders - Bad Manifold?

    PS.... Keep your "auto mechanic" friend away from your boat engine. Other than the basics of what makes engines run, that is as close as these motors come to being alike. Taking his advise in this matter will cost you your motor. If you are in salt water, and you are not doing anything to get rid of the intrusion, your motor may have already suffered irreaparable harm.
    If it were easy, any Caveman could do it.

  8. #8
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    Default Re: Water in Cylinders - Bad Manifold?

    Thanks KaGee - I'll tell him what you said and then give him a good slap upside the head I have already purged the water and oiled the cylinders through the spark plug hole. I am also (probably tonight) using engine flush and then changing the oil.

  9. #9
    Admiral KaGee's Avatar
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    Default Re: Water in Cylinders - Bad Manifold?

    Oil change is a good idea. Those "batwings" are hard to test. But, I'll bet if you pulled the one on the cylinders that had water, you would see evidence of water in the exhaust port.Good luck in finding your problem.
    If it were easy, any Caveman could do it.

  10. #10
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    Default Re: Water in Cylinders - Bad Manifold?

    I did and I did...two of the three ports had minor surface rust.

  11. #11
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    Default Re: Water in Cylinders - Bad Manifold?

    Originally posted by boatgrunt: 1989 OMC with Chevy 4.3 V6 - I have read many topics on the "water in cylinders" problem (which I have). I have also posted a few questions and received helpful responses. Many people suggest that bad exhaust manifolds and elbows could be the potential problem in addition to a blown head gasket. Can someone explain the theory behind how a bad exhaust manifold could leak water into the cylinders? My OMC manifolds are 1 piece meaning that the design combines the function of the manifold and elbow into 1 piece. Inside this part, I assume there are four passageways - 3 for the exhaust gases and 1 for the water. How could the water get into the gas passageways if they are seperate? Even if it did get in through a crack, wouldn't the pressure from the gases blow it out? In addition, some have called to question the exhaust manifold gasket. If this gasket just seals the gases, how could a problem with the exhaust manifold gasket ever lead to water in the cylinder? ...unless maybe condensation or water sprayed over the manifold...

  12. #12
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    Default Re: Water in Cylinders - Bad Manifold?

    Originally posted by Czechmate:
    Originally posted by boatgrunt: 1989 OMC with Chevy 4.3 V6 - I have read many topics on the "water in cylinders" problem (which I have). I have also posted a few questions and received helpful responses. Many people suggest that bad exhaust manifolds and elbows could be the potential problem in addition to a blown head gasket. Can someone explain the theory behind how a bad exhaust manifold could leak water into the cylinders? My OMC manifolds are 1 piece meaning that the design combines the function of the manifold and elbow into 1 piece. Inside this part, I assume there are four passageways - 3 for the exhaust gases and 1 for the water. How could the water get into the gas passageways if they are seperate? Even if it did get in through a crack, wouldn't the pressure from the gases blow it out? In addition, some have called to question the exhaust manifold gasket. If this gasket just seals the gases, how could a problem with the exhaust manifold gasket ever lead to water in the cylinder? ...unless maybe condensation or water sprayed over the manifold...
    Since you NEVER know when the time is up for your cast iron manifolds, the best insurance against rusted cylinders is to take out the spark plugs when you winterize yor motor. I learned this the hard way. I have drained the block for winter in October, but the water leaked to all cylinders 2 months prior to it. Than I did not use the boat 3 years. Now I am replacing engine. So there may be 5 places to drain , but also 8 spark plugs to take out!!

  13. #13
    Supreme Mariner Haut Medoc's Avatar
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    Default Re: Water in Cylinders - Bad Manifold?

    Czeckmate, not sure where you are going with taking the spark plugs out....If you take them out and leave them out you will risk ( no, get)moisture intrusion. If the water leaked in two months prior to your winterization, then it was already a done deal. ..Please elaborate....& welcome to the forum at Iboats. ....JK
    Disclaimer!: In my inexpert opinion......

  14. #14
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    Default Re: Water in Cylinders - Bad Manifold?

    ...maybe he stored it indoors? Thanks for saying something JK - it sounded like a good idea (and it may be in certain situations), but I was about to run home and pull them for the winter; however, I store my boat outdoors, so to your point, I probably would have ruined my engine.

  15. #15
    Supreme Mariner Haut Medoc's Avatar
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    Default Re: Water in Cylinders - Bad Manifold?

    Leaving the plugs out for any length of time regardless of the surroundings is never a good idea. ....JK
    Disclaimer!: In my inexpert opinion......

  16. #16
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    Default Re: Water in Cylinders - Bad Manifold?

    Grunt....you seem to not grasp what is being said here. Your manifolds are rusted out internally. Junk. You cant see where. And don't replace just one, do both. Best to upgrade to centerise, cause the one piece are obsolete. Period. Now, if you got any saltwater in that oil, and if its in the cylinders, it has also leaked down past the rings into the oil. If its saltwater within 24 hours that oil and filter should have been changed, ran with just block water a few minutes, dumped, and done again at least 2 more times. Saltwater sitting in that oil will destroy the motor short order. I just went through this same scenario, and still have one side to do on the mans. Then hoping it WAS a manifold, and not a head related problem, and looking for good steady oil pressure.

  17. #17
    Commander Lou C's Avatar
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    Default Re: Water in Cylinders - Bad Manifold?

    And BTW, if the manifolds are junk, you should not be starting and running it with them on there. Best to see if you can get a new set on there pronto so you can run it and change the oil as many times as it takes to get the water out.
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  18. #18
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    Default Re: Water in Cylinders - Bad Manifold?

    Roger - hear ya loud and clear. I am planning to replace to a merc set of risers and elbow, change oil multiple times and use engine flush.

  19. #19
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    Default Re: Water in Cylinders - Bad Manifold?

    Id check the intake under the thermostst housing for a hole too.
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