I have no experience with salt on boat windshield, but I do have experience on with the glass top on my saltwater aquarium. I don't like to use cleaning solutions around the tank because I am afraid that I will contaminate the fish tank. What I do is use plain water and a straight edge razor blade. I just pick up some replacement blades for a utility knife - they sell these at hardware stores or Wal-Mart. I scrape the wet glass with the razor blade. It works for me. But I don't know what your results may do since your salt is on their very long. If it is not a contaminant on the surface of the glass, but rather an etching or pitting of the glass surface, then you have another problem. You may be able to polish it out if the pitting is not too deep. They sell polishing and buffing material (I think at the auto parts store). Sometimes it is a powder that you have to mix with small amount of water to make a paste. You start with larger grit paste and then work to finer grit paste - much like using sandpaper. But I would not suggest using sand paper, I am afraid it would damage the window so that yo could not see out of it. If the winshield is plastic (acrylic) and not glass, then I sould suggest just replacing it. Hope these ideas help you.
Good Luck, Ray
