Problem is there are urethanes, and then there are URETHANES. Automotive/hardware paints are urethanes, but they are meant to bond to rigid surfaces. That does not characterize a WW raft. The elderly woman at AAA Inflatables told me she applies a flexible urethane all the time, as she reached for her abacus to calculate the mortgage I'd need for her to do the work. Krylon Fusion lasts about a year, by the way. On the other hand, I am getting an indepth education on rafting product fabrics and adhesives, and am confused at a far higher level.