As always, there appear to be quick fixes in a can, but in truth you can't repair a wood boat with an off-the-shelf remedy. Not even close. The rotten wood should be completely removed and replaced in a way that leaves the boat as smooth and strong as new, or else the repair will lead to even more problems.
Boats, like motorcycles, are practically all function. Your boat isn't a car, which has a body that seldom serves the structure.
If you are going to fix the boat intellegently, do it right. Take some very detailed pictures to post here--- enough to explain the problem visually, and then listen to advice from experiennced carpenters.
You can really mess up your boat trusting products like Git-Rot, which could be explained, but suffice to say enough has been written here and elsewhere about how misleading some boat-repair-in-a-can companies claims can be.