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I have a 1962 Sea Coaster which was professionally (one hopes) repaired a couple of years ago. The garboards were replaced and it was suggested that the transom should be replaced at the same time. When all was done I was told that only the outer transom had been replaced because the inner transom was in perfectly good condition. On launching her this weekend I discovered a not insignificant leak through a horizontal seam in the outer transom a couple of inches above the base water line. Looking carefully at that seem from outside the boat, you can see light through it. Before going back to the boatyard to discuss this I was curious as to whether there would have originally been a joint in this location on the outer transom? Again, it is a few inches above the painted portion of the transom. If so, how would this seam have been sealed? Glue? Caulk? Is it a freak occurrence that this seem has opened up a tiny bit at the exact spot where it intersects one of the vertical seams of the inner transom? I sort of anticipate the boatyard telling me this is a tiny gap and should just be filled. Is it acceptable to consider filling this with epoxy or caulking? It doesn't seem so to me, but maybe I'm being overly concerned about this. If so, should the joints between the boards of the inner transom also be caulked? It doesn't appear they ever were. This boat has never leaked in the eight years I've had it. Want to arm myself with more knowledge before questioning the work that was done. Thanks, Rich

Which Thompson company built the boat?

How far above the base of the transom is the joint between the horizontal boards?

Andreas

It is a Peshtigo built boat. I am not in the same location as the boat today, but I guess the joint is about six or eight inches above the base of the transom.

On the transom my Off Shore which is a 1955 there is a joint at the same place as you discribe yours. I think that you will find this joint to be typical of these boats regardless of year built.(Some one will correct me if I am wrong).
I would think that most likely this was glued.

The question that I am asking is if this repair was done a couple of years ago as stated why did the joint just now open up?
Has something changed to cause this? Something structural or something climate related such as it being warmer where the boat is stored.
Could be that is you keep the boat in the water for a while it will swell shut.(Hopefully you have a bilge pump).

As far as the boat shop goes they will most likely tell you to "Fill it". To reglue some thing like this would I believe require you to remove the transom, remove the back bracing and then try to use clamps to bring the joint back together.

Sorry for,the long reply but it is a rainy day here in Northern Michigan and so I am not out on my boat.
Let us know what you fid out.
Karl.

On my '57 Sea Lancer the lowest horizontal transom plank is about 8 inches. On the '56 or '57 Off-Shore and the '59 Off-Shore Cabin Cruiser that bottom plank is 12". These are all Peshtigo built boats.

The transoms are stained and varnished on the above boats. No paint. Looking at the 1962 brochure, it appears as if copper bronze bottom paint was used on the lower portion of the transom on all the boats.

You may be able to squeeze some caulk in the gap. Use a flexible marine caulk and try to inject it with a needle to get it way in there. I would not recommend a hard epoxy.

Andreas

Thanks for the reply, Karl. I thought I remembered there being a joint in that location on the original transom but wasn't sure. As to your question, I can't really identify a reason why this might have happened. The boat is in good shape, there are no apparent structural problems in any parts around the transom. Nothing particularly different about use or storage this past year. The only thing thats a bit unusual is that the boat has not been in the water yet this year and has been outside in the sun (mooring cover on) for two months of this hotter than normal summer. I'm sure you are right about taking the boat apart to re-glue the joint. I'm sure the yard is not going to want to accept responsibility and do all that work gratis. I'm wondering if it could be filled with epoxy, it's not all that wide a gap, maybe 3/32. Or is that a bad idea? Curious what anyone thinks.
Rich

Thanks, Andreas. I think you and Karl have confirmed that they made my new outer transom in the same way as the original. I don't know if my Sea Coaster ever had bottom paint, but when I got her the hull was painted all white, and as you say, the very bottom of the transom was painted up to the waterline, the rest varnished. If the yard that did the repair is unwilling to address this problem in another way, I guess I will just have to try and fill the joint. Sounds like you think that is ok. I will take your advice and avoid epoxy. Should I use 3M 5200? I know you sometimes counsel against adhesive caulk in case something needs to come apart in the future, but I can't see why this joint would ever need to come apart.
Thanks, Rich

3M 5200 is fine in this application, in my opinion.

On thought. Squeeze it in from the interior of the boat????? Not sure what type of splash well this thing may have, but if it's easily removed and the motor is removed, you can unscrew some of the interior vertical boards. Squeeze in the caulk from the interior. This may reduce and visual harm to the outside of the transom.

Andreas

The transom on my Off Shore has a paint line running across the bottom of the transom as well.
I didn't think that it was original but when I went to strip the bottom that old lead based copper bottom paint was stuck like glue , so it still has a painted transom bottom.(Just fresh paint).
I agree with Andreas inregards to using caulk to fill the joint. If you can get at it from the back that would be great.
If you have to do it from the front I would tape off on either side of the crack and force the caulk into the crack with a putty knife or my thumb. Scrape away as much as you can and then Pull the tape while the caulk is still wet. Down and away from the crack on the bottom side and up and away on the top side.
I would most likely use Boat Life mahogany colored caulk as you can sand this after it has cured if you have to.
Karl.
p.s. Resist the urge to touch the wet caulk after you have pulled the tape.

Thanks for the information and advice, gents. I'll look into what is involved in getting to this joint from inside the boat.
Rich