When we bought our boat we noticed a patch job on the seam, at the very stern of the boat. After 7 years, I've noticed the patch is no longer water tight. I have been looking over some sites for simple ways to patch it from the outside, and I'm wondering what suggestions people may have. I'm leaning towards either JB Marine Weld or 3M 5200. Which of these would you prefer, or is there a better product out there?