Old Town repair putty, Failed

Bought a tube of repair putty (MA-300) from Old Town and used it on my Polylink boat. I was careful to follow instructions: sand, clean and polarize the area before mixing up the two part adhesive. It peeled off after about 3 trips on the river. The crack is inside the cockpit just in front of the seat. This part of the hull will flex a lot and the repair had no flex at all, so it just peeled off around the edges. It would probably work if used to repair an area that doesn’t flex during normal use but it didn’t hold up in this case.

Epoxy Putty
I have used epoxy putty that I buy from my local hardware store on royalex boats. It comes in what looks like two 35 mm film canisters - one has black paste, the other white paste. Scoop out equal amounts and blend (it turns grey). Apply neatly, smooth well before it sets. I’m not sure what it’s normally used for for.

I don’t know if it will work for you. You may have the same problem. But so far it has worked for me on royalex canoes.

Ken this isn’t a Royalex boat.

flex agent
Think a flex agent used by body shops when they paint the plastic bumpers on cars would help take the rigidity out of the putty?