I was able to easily remove old vinyl lettering with just a single edge razor blade. No heat gun needed, no gelcoat damage. In a similar thread, I read where someone filed down the corners of a blade to lessen the chance of damaging the gelcoat. The area under the letters was raised and a slightly different color, so I used some compound to try and even things out. Be careful, as you can easily make the compounded area a different color than the rest of the hull. After some mild compounding, I elected to let the sun do the rest of my dirty work. After only one season, the color was almost uniform; after two, the old lettered area was indistinguishable in color from the rest of the transom. The raised area will probably always be there somewhat, but you can't tell from more six feet away.