I've sprayed some boats with 303 and successfully varnished them later. As long as it was just 303 you used and not silicone, I would not worry about it. Washing the boat down with a strong cleanser and water may well be sufficient to get rid of any residual 303.

: At the suggestion of an experienced woodworker on a kayaking listserv, I put
: 303 on the deck of my Betsie Bay boat. It needs refinishing, which is to
: happen in July, and the silicone was recommended as an interim way to
: prevent UV degradation. I've just learned from Betsie Bay that this was
: about the worst thing I could have done to the boat as it will is
: well-nigh impossible to remove and will make the future finish bead up
: instead of holding to the deck.

: Does anyone have any suggestions for how to get it off?