Marine polyurethane is designed to be used on fiberglass. Fiberglass bends and flexes much more than the sheet metal on your car. In addition, marine polyurethane is made for the marine environment. Last I checked, your car is not...
Have to disagree with you there. The sheet metal will flex a lot more than fiberglass. Might end up with a dent but the paint will be fine . Fiberglass if bent or flexed will crack , that how you end up with spidercracks.
we go thru about 900-1100 gallons of paint a year on yachting equipment. I can tell you from a UV/Environmental standpoint, automotive paints do not hold up more than 5 years. Marine paints will last 20+ years (or until the yacht owner paints the boat another color)
I'm in the Sign and Graphics business. If you want a black stripe down the side of your boat, consider 3m Controltac vehicle wrap. We do a lot of boat graphics. It is a lot cheaper than paint, holds up well for years and is Removable if need.
