Help ... Transom problems

[xTomKx]

We have a 96 Bayliner Cierra and had it repowered about 6 years ago. Went with a big block and Bravo 3. All was good until this year where it started seeping in water into the engine compartment. It was minimal at first but recently got worse so we decided to take it into a local shop. The shop found bubbles coming out around the Gimbal Assembly but there wasn't much room to pinpoint the source so it was decided to pull the outdrive and motor.

After pulling out the Gimbal housing the Transom has a bow in it. It's hard to see in the picture but there is a 3/16 gap between the ruler and the Transom about the middle of the key hole. I am no expert but the Transom doesn't look rotted. Shop is telling us to get a fiberglass expert and build up the material to flatten out the transom. We are a little skeptical. So we are wondering

What is the cause of this issue?

Is redoing fiberglass going to fix it?

 

[jbcurt00]

Re: Help ... Transom problems

Hmmm

Why is the transom both blue & white? Painted gelcoat?

I've never seen a keyhole w/ slathered w/ whatever's coating the interior edges of it. What is that?

I'd check your motor mounts and the transom plywood for water intrusion.

The garboard drain plug seems to have some scrapping damage around it, and some sort of sealant squeezed out from behind it.

Is the thickness dimension of the keyhole still 2-2.25" thick? Consistently even around it's entire perimeter? Was it at the time of the repower?

 

[tpenfield]

Re: Help ... Transom problems

I would seek to find out why the transom bowed. If you do not, then your transom idea will probably be a temporary fix.

as mentioned, I would look to the engine mounts and the stringers that they are attached to, as well as a thorough inspection of the transom core.

 

[xTomKx]

Re: Help ... Transom problems

Hmmm

Why is the transom both blue & white? Painted gelcoat?

I've never seen a keyhole w/ slathered w/ whatever's coating the interior edges of it. What is that?

I'd check your motor mounts and the transom plywood for water intrusion.

The garboard drain plug seems to have some scrapping damage around it, and some sort of sealant squeezed out from behind it.

Is the thickness dimension of the keyhole still 2-2.25" thick? Consistently even around it's entire perimeter? Was it at the time of the repower?

Bottom was painted some years ago when it was in salt water. When it got put into a lake we no longer painted the bottom. What you see is the remains of the paint.

I don't know much about boat hull structure but was told that everything was well at the time it was repowered.

We will check the thickness of the Transom around the key hole.

 

[jbcurt00]

Re: Help ... Transom problems

If it's not 2-2.25" there's something amiss. If it's not really really close to the same all the way around, somethings amiss.

If you can, I'd also remove that stuff slathered on the side of the keyhole. That area is a great window into the condition of the transom. Having whatever it is, covering that area, isn't typical. I wonder if it was added at the repower & why....

 

[Bondo]

Re: Help ... Transom problems

If it's not 2-2.25" there's something amiss. If it's not really really close to the same all the way around, somethings amiss.

If you can, I'd also remove that stuff slathered on the side of the keyhole. That area is a great window into the condition of the transom. Having whatever it is, covering that area, isn't typical. I wonder if it was added at the repower & why....

Ayuh,..... Welcome Aboard Tom,.... I, like jb, wonder more 'bout what was done when the swap was done,....
Were the proper inspections, 'n measurements done,..??
Was the any bow in it then,..??
What "Other" work was done,..??

While I usually seal that area, when I'm doin' transoms, or power swaps,...
That coulda been put there to hide/ try to fix, an already rotten transom,...

When mountin' a Merc, ya need 2", true, even, parallel for All the area contacted by the inner, 'n outer transom assembly,...

 

[xTomKx]

Re: Help ... Transom problems

The mechanic that did the repower was a friend so I doubt that he would hide or mask any issues. I do not know if the thickness of the transom was checked but the boat has been in the water for 6 years since the repower without any major issues.

My untrained eye did not see any rot in the transom. What is the best way to test the condition of the transom?

 

[jbcurt00]

Re: Help ... Transom problems

If the water was coming in around the keyhole, and the keyhole is now deformed, I suspect probing the plywood exposed in the keyhole would be where I started.

That will necessitate removing whatever that stuff is, as I mentioned. What is it?

 

[britisher]

Re: Help ... Transom problems

Water gets in from the outside, not the inside. Whilst the transom may be 'bowed' on the inside, it should be flat on the vertical outside where the gimble housing bolts through. Sealing that gap between gimble and boat transom is the rubber gasket on the gimble housing. These gaskets flatten out over time and allow water to seep past and in through the keyhole. Also, that water will also make its way into the wood of the transom and hey presto, you have a rotten transom.
I would suggest you replace first the gimble housing rubber gasket (I think they are like $15.00), then check how flat the outside vertical of the transom is that the gimble housing bolts up to. If it is flat, then you need to level out the inside part of the transom, but first make sure there is no rot in the wood. If there is, then you are into repairing or replacing the wood transom.
The PO on my own boat had not bothered replacing the gimble housing gasket and simply used caulk around the housing. Being new to boating I did not realise the significance of that, but my boat mechanic did. I had one mushy transom.

 

[xTomKx]

Re: Help ... Transom problems

If the water was coming in around the keyhole, and the keyhole is now deformed, I suspect probing the plywood exposed in the keyhole would be where I started.

That will necessitate removing whatever that stuff is, as I mentioned. What is it?

My guess is that it's some type of sealant to help preserve the transom in case of a leak. If we poke it with a screw driver in the key hole and the bolt holes for the gimble housing will that be enough to detect rot?

Water gets in from the outside, not the inside. Whilst the transom may be 'bowed' on the inside, it should be flat on the vertical outside where the gimble housing bolts through. Sealing that gap between gimble and boat transom is the rubber gasket on the gimble housing. These gaskets flatten out over time and allow water to seep past and in through the keyhole. Also, that water will also make its way into the wood of the transom and hey presto, you have a rotten transom.
I would suggest you replace first the gimble housing rubber gasket (I think they are like $15.00), then check how flat the outside vertical of the transom is that the gimble housing bolts up to. If it is flat, then you need to level out the inside part of the transom, but first make sure there is no rot in the wood. If there is, then you are into repairing or replacing the wood transom.
The PO on my own boat had not bothered replacing the gimble housing gasket and simply used caulk around the housing. Being new to boating I did not realise the significance of that, but my boat mechanic did. I had one mushy transom.

To clarify things, the bow is in the outside of the transom. The boat is at the mechanic right now which is far away and we weren't able to get down there to verify the thickness of the transom yet or condition of the hull/motor mounts. Should have that info sometime this week.

The amount of water getting into the hull was minimal. It was pumped out once a week with the bilge pump. I am hoping it wasn't enough to ruin the transom.

 

[jbcurt00]

Re: Help ... Transom problems

The transom should be flat across the keyhole vertically & horizontally. There's a reason it isn't, not sure what that is, but it shouldn't have a bow in it. If it isn't flat, as mentioned earlier, you'll have a hard time getting the OEM gasket to seal the transom plate against the transom.

If the transom bow is ONLY on the exterior side, that suggests that the transom has compressed. Otherwise the exterior bow should cause a similar sized hump on the interior.

If we poke it with a screw driver in the key hole and the bolt holes for the gimble housing will that be enough to detect rot?

Perhaps, you might consider pulling any screws or bolts thru the transom & checking there too. Water sealed between the inner & outer transom skins could travel quite a ways before it developed any rot. But yes, the keyhole & transom plate holes would be a good start. Again, check w/ the guy that did the repower & confirm what & why he added the sealant to the keyhole. If the transom was 100% & he added it to keep any future problem from allowing water to contact the wood, great.

The amount of water getting into the hull was minimal. It was pumped out once a week with the bilge pump. I am hoping it wasn't enough to ruin the transom.

Weekly may have been enough to minimize a problem, but how long has it been leaking w/out collecting enough water to be noticeable in the bilge? Most water intrusion problems do not develop quickly or overnight. It often starts small enough to be extremely difficult to detect. By the time it's noticed, it's a larger problem.

If you remove all the sealant added to the keyhole & do a thorough inspection, if there are no problems, you can (and should) reseal it before you reinstall the motor & outdrive.