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Transom Seal


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I’ve had water slowly seeping in on back wall of the port side visible when you look under the motor.  My mechanic figures it’s a transom seal.

Anybody here have experience with replacing those on a 2005 Chap 270 Signature with twin 4.3’s and Bravo 3’s?.  Wondering what’s involved (time & materials) and if there are any “trap doors” I should be concerned about falling into?
As always, I appreciate any and suggestions.

Wingnut??

 

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Yes.  Now that you mention it, a number of years ago we stuck a rock about the size of a minivan with the port drive.  Both drives were trailered all the way up as we were just “crawling” into the bay at my in-laws place where we used to dock.  

It was very high water in the spring and the homemade markers we used were temporarily submerged.  With the drives all the way up there was no evidence of physical damage like you would expect such as an oil slick, skeg or prop damage or vibration.  I’ve even done pressure and vacuum tests on both drives to ensure the seals were still intact and both drives passed those tests.

Maybe that could have caused the port drive seal to shift?

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2 hours ago, KDV said:

I’ve had water slowly seeping in on back wall of the port side visible when you look under the motor.  My mechanic figures it’s a transom seal.

Anybody here have experience with replacing those on a 2005 Chap 270 Signature with twin 4.3’s and Bravo 3’s?.  Wondering what’s involved (time & materials) and if there are any “trap doors” I should be concerned about falling into?
As always, I appreciate any and suggestions.

Wingnut??

If it is in fact the transom seal, then it's a bit more involved if I'm not mistaken.  You'll obviously need to pull off the outdrive, then in order to remove the transom assembly unit which has the seal on the back of it and is up against' the boat's transom, you need to un-bolt it off of the inner transom plate (inside the boat on the inside of the transom) which the engine also sits on that plate.  Hence why the engine also needs to be removed.  The Volvos are just as tedious also. 

So you have the engine sitting on that inner transom plate (the plate acts as the rear motor mounts for the engine) and unbolt it off the plate to free it.  Then you can unbolt the 6 bolts of the exterior transom assembly that go through the transom and the bolts are tightened up against that inner transom plate to remove the transom assembly and access the back of it where the seal is.  I believe there is an indent all around the back of the transom assembly for that seal to sit in.  You also have to pull off a few of the other items like the cooling hose, the exhaust hose, the shift cable etc.  Unfortunately it is quite the operation.  Anyone can correct me if I'm wrong.  

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22 hours ago, KDV said:

Yes.  Now that you mention it, a number of years ago we stuck a rock about the size of a minivan with the port drive.  Both drives were trailered all the way up as we were just “crawling” into the bay at my in-laws place where we used to dock.  

It was very high water in the spring and the homemade markers we used were temporarily submerged.  With the drives all the way up there was no evidence of physical damage like you would expect such as an oil slick, skeg or prop damage or vibration.  I’ve even done pressure and vacuum tests on both drives to ensure the seals were still intact and both drives passed those tests.

Maybe that could have caused the port drive seal to shift?

Back in the 80s i hit a railroad tie with an out boar and i have to replace the transom. Good luck.

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8 hours ago, KDV said:

That does sound very involved and labour intensive.  Thanks for the feedback.  I guess I’d better start saving my pennies...

Just be as sure as possible that it is in fact the transom seal and not one of the items that @Bt Docturmentioned.  Those are also culprits to many a leak stories and MUCH MUCH easier to replace/fix than the transom seal.  You also mentioned that the rock you hit was a couple of years prior to noticing the leak happening, which doesn't sound like it's related to the leaking since it most likely would've started leaking almost immediately after hitting the rock and not a few years later.

Take a closer look at the different bellows coming through the transom and see if the leak is in one of them first before going ahead and having all that costly work done.  One of the most common places in those Bravo Shmavo Mercury Mcchmurkey lol is the pivoting pin!!!  Do a search for that on this forum and see how many people have had the pin rust out and leak water into the transom and then use that special kit to replace it.  Ask your mechanic to start with that and then check each of the other items.

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I just did this job on a 2001 Chap 300. Once the motors were out it was pretty easy to get the transom assemblies out. Here are some things that come to mind:

 

  • Once the motors were out, the transom assemblies were straight forward to get out. 
  • I disconnected the trim hoses at the pump, then pulled the assembly out with the hoses attached still. It was easier to feed the hoses through on the bench vs the bottom of the boat. 
  • I replaced the fitting for the gear lube bottles- they are 11 bucks and it will never be easier to replace them. 
  • My gimble ring and swivel pin were in TERRIBLE shape. On both motors. That is where my leak was coming from. Replaced with new gimble rings and stainless swivel pins. $$$$ that I did not plan on. 
  • While I had it apart, it had my fiberglass buddy come by. My transom was solid but we laid down some resin an new gelcoat while it was apart. 
  • The assembly was pretty straight forward. A two person job. Use black weather strip adhesive on the transom seal. Coat the transom assembly and the seal. Let them tack up, then put the seal in the groove. If you rush it, or don't do this, you will have a hard time keeping the seal in place. 

 

I somehow got the sides mixed up- so I had to move the speedo hose. That was my only real obstacle other than spending more money. I ended up doing the bellows too while it was out.  

 

Let me know if you have any specific questions. Unfortunately I did not take any pictures- but it is fresh in my mind. I suspect your swivel pin is pretty rusted too and lets water in. It is a very common problem. 

 

Aaron 

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On 1/11/2021 at 6:34 PM, Hatem said:

Just be as sure as possible that it is in fact the transom seal and not one of the items that @Bt Docturmentioned.  Those are also culprits to many a leak stories and MUCH MUCH easier to replace/fix than the transom seal.  You also mentioned that the rock you hit was a couple of years prior to noticing the leak happening, which doesn't sound like it's related to the leaking since it most likely would've started leaking almost immediately after hitting the rock and not a few years later.

Take a closer look at the different bellows coming through the transom and see if the leak is in one of them first before going ahead and having all that costly work done.  One of the most common places in those Bravo Shmavo Mercury Mcchmurkey lol is the pivoting pin!!!  Do a search for that on this forum and see how many people have had the pin rust out and leak water into the transom and then use that special kit to replace it.  Ask your mechanic to start with that and then check each of the other items.

Good points.  Actually did replace both steering pins using those kits about 3 years ago because there was evidence of water getting in there and some corrosion on the pins. Used an endoscope camera to verify the water intrusion.  All bellows were replaced at that point and further endoscope imaging showed the bellows areas to be dry as a bone after the job was done.  So at least that is a positive...

As for water ingress into the transom...I’m planning to check the transom area with a moisture meter in the spring after it has had the opportunity to dry out completely over the winter and see what I end up with.  I just have to do some research to find out what the acceptable moisture specs are supposed to be.

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