leaky transom

Rebuilt transom on 16 foot Grady White. Looks tight but have small pin hole leak somewhere. I have tried caulking entire seam with Boatlife Life Caulk and after that didnt work with that spray stuff they advertise on TV. Neither worked. Leak very small and does not stop me from using - bilge never kicks on - but frustrating as would like to be water tight. Because transom consists of inner wood and outer wood it is impossible to tell exactly where leak is on outside. Any ideas as to another product - dont want to take apart again!

 

If this is a wood boat, a slight leak is to be expected. I'd stay right away from any miracle stuff sold on tv!
Few motor boats built that way can be expected to be completely water tight.

 

Pull the boat out of the water and pour a 5 gallon bucket of water, with food coloring die in it and see where it comes out.

 

If part of the transom has wood in it you better find the leak or you will be repairing it again. The leak must be below the water line I would guess. This method would be a pain but I assume if you have rebuilt the transom you have already gone through the painting/gel coat process. Without knowing more of what you did to fix it its hard to say but more than likely a seam is leaking. Try using some fiberglass tape and epoxy it on all seams below the water line. Fill the weave and build it out past the edge of the seam. Fair it out and re-finish. You need to fix it from the point of entry, fixing it from inside will not prevent futur problems IMHO
Feel free to send me. PM with contact number I'd be glad to discuss. I am no expert but have built several boats and just starting a 28 foot off shore fish killing machine.

 

I replaced entire lower transom along with some lapstrakes. Used 3M 5200 to seal lapstrakes and garboards to transom, along with screws. I am told that once 5200 is used, it stays glued so no way i am going to try to take apart and reseal. Small leak definately below water line in corner. Used Boat Life caulk along entire exterior seam, which I think reduced leak but still there. I have been told not to use fiberglass and epoxy because it is not flexible enough for wood expansion, movement etc. I had thought of that and am still open to it if you have had success. Thought there might be caulk type product that would get more into the seams than the boat life. I can live with the leak but really would like to conquer it!

 

I did not realize it was lap strake construction. Not real familiar with it but allowing for the wood to move sounds like a good idea. 3M 5200 is real good stuff not much better that I mad aware of. I can't offer any good advice for lap strake never been there before but do plan on it someday.

 

I don't use 3M-5200 below the LWL on wooden surfaces, because it can release, unless installed under pressure and remaining so until fully cured (a few weeks). I've seen 5200 pull right out of underwater lapstrake seams like rubber string.

BoatLife is nearly useless under the LWL. The preferred product under the LWL on wood, is polysulphide (3M-101 or similar). This assumes the wood isn't encapsulated.

I've done a lot of lapstrakes over the years and 3M-5200 is a pain in the butt to remove, but not imposable. If you're aware of it, you can take precautions to safeguard against damage to the faying surfaces. A hot knife is one method. The usual course of action is to renew the general area's faying surfaces. This means opening up the laps and gains around the area, faying surfaces on the transom frame, cleaning these surfaces, then refastening with a new batch of goo. It's probable that a fastener was missed or has come loose and it's leaking past it. It easy to miss one out of several hundred (small boat) or a few thousand (25' boat). While the planking is freed from it's bonds, check each fastener hole, repairing and restoring those that might need it. These and of course the seams are the leak points. Seams are usually pretty easy to see, but a bad fastener will drive you nuts, trying to find and why I suspect this is what it is. I know it sucks, but it's not as uncommon as you might think.

 

Thanks. I will try to 3M-101. If it doesn't work, maybe next year I will take apart but don't have energy now. Only small leak and boat is trailered so I can live with it. Thanks to all who took time to post.

 

Smearing goo in a tube into a seam usually doesn't fix anything, though often it will hide the leak for a little while. Most all lapstrake leaks can be traced back to fasteners, permitting the planks to "work" along the seams.