In a conflict between vinyl signage plastic stick-on material vs. UV, the later will always win...
(Maybe not a problem for a power boat kept in a garage on land or in a boathouse on the water.)
It would be kinda like all those stick-on graphics that car/truck builders used to put on their fancy kid-oriented models a few years ago. Remember how fast the sun would lift the edges and expose the glue? To be fair, the large vinyl side graphics on my '80 Sundowner model Mazda truck *did* make it to eight years looking OK, and then I sold it. That truck did not have vinyl on the hood to curl and peel, like the Toyota 4X4's did, though...
Just be prepared for a horrible/massive cleaning and maybe a sanding/painting job to get rid of the glue residue someday down the ol' watery road.
Sorry to be a bit cautionary, but you seemed to be soliciting "opinions"...
Loren