I used this to patch some holes and cracks on my scout. I then sanded it down and put fiberglass tape over it and along the hull for more durability. It holds and I use this a good but on stuff around the house.
only bad this is is that once you mix the hardener in you have about 10 minutes tops.
Recommended as a fairing compound for a cast iron keel on a sailboat by the local expert West Marine sales rep. The product went on quickly, stuck very well to bare cast iron, and was ready to sand after just 1 hour. I hope it last since swing keels are hard to get to when the boat is on the trailer.