I realize that this is too little, too late, but washing the boat with lacquer thinner or acetone, followed by scraping rather than sanding would likely have eliminated the problem. Scraping removes the finish without pushing any surface contaminants into the wood. Once the top layer with the 303 was removed, you could sand to fair the surface.

I wonder if perhaps the poor condition of your boat's finish might have allowed the 303 to penetrate deeper than it would on a new finish?