I would discuss this with the flex seal manufacture, than the boat manufacture first. A boat is a expensive thing to experiment on so I would get both manufactures okay first. I have used it to do a quick fix on a fiberglass boat with a leaking crack in the bottom. I still have not done a final repair two years later. Had a pvc drain pipe crack, painted it liquid flex seal 5 years ago, still holding as of today, so it might work. I do carry a flex seal tape roll in my repair kit as a emergency back up for a "if all else fails" fix. It is like duct Tape and bailing wire, don't leave home without it. You might get by better using it on your oar frame, not the raft its self.
Time is like a river. You cannot touch the water twice, because the flow that has passed will never pass again. Enjoy every moment of life on or off the river.