I can't dispute what Paul and Brian mentioned, but also consider that salt is a corrosive. It may not have a negative impact on the wood or the figerglass, but what else might you have in or on your boat that could corrode? Any hardware like screws or bolts, a rudder system, etc?

I rinse my store bought boats (still building my first strip built boat) after every use, because if I don't, they get gritty. The salt content here is high, and you can litterally wipe up the salt after the water has evaporated. It gets into everything... PFD, spray skirt, deck bag, etc. It's just a nicer boat without all the grit.

Oh, and do it at the ramp (to some degree) if you can. When I put my boat on my homemade rack attached to my pick-up, the salt drops off into my bed (no bed liner) and I learned that the salt collects and corrodes my truck. Opps. If I can't do it at the ramp, I spray my truck down when I get home, along with the boat and ALL the gear I had with me.

Rick