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  1. #1
    Seaman
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    Default Leak around the transom

    I have a leak coming in around the bottom of the transom it just trickles in. I replaced the drive bellow last year and the shift cable looked good. I may have not got the drive bellow sealed correctly, but if it was the drive bellow wouldnt it leak in around the drive shaft? It comes in at the bottom of the transom plate. Any suggestions?

  2. #2
    Rear Admiral Fishermark's Avatar
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    Default Re: Leak around the transom

    Is this a Mercruiser? The bad news? Chances are good your transom is rotten and leaking.

    Could also be the lower bolts - which are an aluminum alloy - are corroded out and leaking. But if they are, then your transom itself is probably shot too.

    It could also be the exhaust pipe - where it connects with the transom plate.... but either way, the engine has to come out to fix.

  3. #3
    Lieutenant Commander proshadetree's Avatar
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    Default Re: Leak around the transom

    Thats what happened to my baylinner. When I pulled her apart rotten at the lower section. I hape its you exhaust gasket or a lose bolt.

  4. #4
    Moderator Bondo's Avatar
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    Default Re: Leak around the transom

    Ayuh,... 9 times outa 10, it's a Rotten transom....
    Any Grease is Better,..... Than No Grease at All.......

  5. #5
    Seaman
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    Default Re: Leak around the transom

    thanks for the info

  6. #6
    Seaman
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    Default Re: Leak around the transom

    Yes it is a mercruiser, is there anyway to tell if the transom is rotten or if the exhaust pipe is bad with out taking the motor out? I just dont want to put alot of money in it but if its something some what easy to fix I would do it.

  7. #7
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    Default Re: Leak around the transom

    Take a mirror and poke it around by the suspect area where it's leaking and see if you can find it,,, while the boat is in the water. If a mirror is too hard to see that far down, try poking a digital camera down there and snap a bunch of pics.

    As for the leak, I don't think you have an easy fix there... bellows, transom seal/rotted transom, exhaust seal. None of these are easy fixes. About the only "easy fix" would be if the tilt-trim hose manifold is leaking, but that would be on the bottom of my list of suspect areas.
    2001 Crestliner SuperHawk 1800, Mercruiser 140HP
    2007 Tracker 1436 jon boat, 7.5HP Force

  8. #8
    Lieutenant Commander proshadetree's Avatar
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    Default Re: Leak around the transom

    I put mine nose up and filled the bilge with water. Did not come even close to the drive shaft. It leaked on the outside at lower transom. Took it apart and it was rotten.

  9. #9
    Seaman
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    Default Re: Leak around the transom

    It very well could be the transom because this fall when i noticed it leaking it was trickling in between the inner plate and the transom. I figured if it was the drive bellow leaking then it would come in around the drive shaft. Just the joys of owning a boat...lol

  10. #10
    Petty Officer 1st Class Brentathon's Avatar
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    Default Re: Leak around the transom

    I had a very small trickle leak that I was barely able to see....it leaked from the very bottom of the transom plate.......YET, it is simply the Upper Swivel Shaft seal that's leaking, as it's wet in the area where the steering lever goes through the transom....the water just happens to run down (I don't know exactly how), and appears to leak from transom plate.

  11. #11
    Cadet scubapro69's Avatar
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    Default Re: Leak around the transom

    I have a 1990 17' sunbird and i had the same probem when i bought the boat. I took to several shops and they said the transom was great. Thank god. I went ahead and opted to seal around the drive with a sealer called Thermo Plastic by a company called Nuflex instead of pulling the motor and drive. Has worked excellent for over a year.

  12. #12
    Honorary Moderator Emeritus Don S's Avatar
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    Default Re: Leak around the transom

    I went ahead and opted to seal around the drive with a sealer called Thermo Plastic by a company called Nuflex instead of pulling the motor and drive.
    That is a bandaid stuck on a bullet wound. Fixes nothing, but may of stopped the bleeding for a short time.
    The only way to fix the problem is to pull the transom shield and put in a new seal.
    It's also very possible the exhaust Y has corroded through where the seal ring goes, or a tab has corroded and broken off. Either way the engine has to come out to actually locate the problem.
    I have pulled many engines, put the drive back on. Plugged the exhaust Y, strapped the boat to the trailer and backed them down in the water and crawled into the engine compartment where the engine was and actually looked for and found the leaks.
    Don S.


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  13. #13
    Seaman
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    Default Re: Leak around the transom

    Ok I have got some good things to look at as soon as the weather gets a little better. More than likely I can rule out the drive boot and the shift cable boot leaking right?

  14. #14
    Lieutenant Commander proshadetree's Avatar
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    Default Re: Leak around the transom

    Raise front of boat. Water the bilge, and look in the back. Dont go over the lower access of the drive shaft. I have found several leaks this way. and I dont have to haul to lake.

  15. #15
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    Default Re: Leak around the transom

    Quote Originally Posted by Brentathon View Post
    I had a very small trickle leak that I was barely able to see....it leaked from the very bottom of the transom plate.......YET, it is simply the Upper Swivel Shaft seal that's leaking, as it's wet in the area where the steering lever goes through the transom....the water just happens to run down (I don't know exactly how), and appears to leak from transom plate.
    +1. This was my leak. Well, one of my leaks.
    If it ain't broke, it will be after I do this...

  16. #16
    Seaman
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    Default Re: Leak around the transom

    Ok well I finally got my boat in the shop and was working on it trying to find out where my leak was coming from. After checking the bellows and other items I found that one of my bottom transom plate bolts was about a quarter of the way loose. I haven't put it in the water to check it yet, but I'm almost certain that is why it was leaking. Thanks for everyones help and advice.

  17. #17
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    Default Re: Leak around the transom

    But why is it loose, thats the question you have to ask yourself.

  18. #18
    Rear Admiral Fishermark's Avatar
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    Default Re: Leak around the transom

    Quote Originally Posted by Jamz3333 View Post
    one of my bottom transom plate bolts was about a quarter of the way loose.
    I've never seen one simply come loose. I have seen them get loose because the transom was rotten and soft enough to compress.... that causes the bolt(s) to be loose. Sorry.

  19. #19
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    Default Re: Leak around the transom

    What are you working on there, a Mercruiser yes, but what is the year or better yet, what is the S/N?

    Quote Originally Posted by Jamz3333 View Post
    I found that one of my bottom transom plate bolts was about a quarter of the way loose.
    My .02$ guess is the lower bolt is corroded and broken. If that's the case, I bet the transom is shot.

    But, that's just a guess as we don't know exactly what you are working on; M1, Alpha1, Alpha1 GenII, Bravo 1-2-3
    2001 Crestliner SuperHawk 1800, Mercruiser 140HP
    2007 Tracker 1436 jon boat, 7.5HP Force

  20. #20
    Seaman
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    Default Re: Leak around the transom

    It is a mercruiser alpha one gen 2. I have never dealt with a rotten transom but when I tightened the bolt up the transom didn't give at all it just tightened back up. I'm not sure if that means anything or not. It is also a 1991.

  21. #21
    Rear Admiral Fishermark's Avatar
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    Default Re: Leak around the transom

    Quote Originally Posted by Jamz3333 View Post
    when I tightened the bolt up
    How did you tighten it? I'm not 100% sure on the gen 2's, but on an Alpha, the lowest two bolts are actually carriage style blots that fit into a square hole on the transom assembly and the nut is on the inside of the boat. There is also a stud that goes aft for a zinc.

    Here's a pic:


  22. #22
    Seaman
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    Default Re: Leak around the transom

    Quote Originally Posted by Fishermark View Post
    How did you tighten it? I'm not 100% sure on the gen 2's, but on an Alpha, the lowest two bolts are actually carriage style blots that fit into a square hole on the transom assembly and the nut is on the inside of the boat. There is also a stud that goes aft for a zinc.

    Here's a pic:

    It is a carriage style bolt. I just come from the inside and tightened it with a socket. I couldn't see the other bolt due to the exhaust being in the way so I will have to figure something out there. Hopefully it's not loose though.

  23. #23
    Honorary Moderator Emeritus Don S's Avatar
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    Default Re: Leak around the transom

    If the one you tried was loose, the transom is rotten. Those bolts just don't come loose. They have Nylon lock nuts on them.
    You also have a Gen II drive, no through bolts.
    Don S.


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  24. #24
    Seaman
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    Default Re: Leak around the transom

    Quote Originally Posted by Don S View Post
    If the one you tried was loose, the transom is rotten. Those bolts just don't come loose. They have Nylon lock nuts on them.
    You also have a Gen II drive, no through bolts.
    The nut that i tightened didnt look like a lock nut. would there be a chance that who ever had the boat before me put a different nut on it? the bottom of the transom bolt is a carriage style that goes through the transom plate. if the transom is rotten would it have any give to it? like if you pushed on it or put pressure on the outdrive? ive never had to deal with a rotten transom so i dont know how this works.

  25. #25
    Seaman
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    Default Re: Leak around the transom

    Earlier in this post I said that the leak was coming in between the transom plate and the transom, well I took it to the lake and I saw that it is actually coming in and running down the inner transom plate. Now its not leaking around the driveshaft so I dont think it is the drive bellow. So it is somewhere in between Im guessing. Besides the transom being shot (which I hope it's not) Where else would water come in at? I also noticed when a wave hit the back of the boat water would rush in more sudden than as if it was just sitting in calm water.

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