Hi, I have tried to search, but "leak" brings up a lot of results on this site which aren't this problem!
I have an old zodiac which I brought cheap. It leaks around the transom. From what I can tell you are pi**ing into the wind trying to seal this, so the transom would need to come off and be stuck back on. I can find quite a lot of info on this little problem - it seems to be £100 or so to pay someone, or a DIY job for the brave.
I have a second issue that I have found. When I pump up the tube on one side, the other side inflates. So the bulkhead between the two tubes must have separated. Well....I assume it must be a bulkhead, I don't even understand exactly how its constructed. Can this be repaired?
I am starting to think that I need to throw it in the bin!
I forgot to add, the tubes hold air ok, for at least a couple of weeks. My concern is that the boat is considerably less safe with effectively only 1 tube. If I get 1 puncture, the whole boat goes flat!