To expand on the good advice already posted, if you're working with a gelcoat base, you may want to sand the transom after you remove the old name. If your fiberglass is at all oxidized, the old name will leave a high gloss artifact you'll see under the new name. Sanding will insure the surface is uniform.
Wet sand the entire transom with a rubber block and 600 grit, add a few drops of Dawn to your wet sand bucket to keep the paper from loading and provide a little lubricity. Sand in a cross hatch "X" pattern. Wash off the residue, then buff out with a wool pad buffer and gelcoat compound. Final clean with denatured alcohol, then do the application of the new name.
Patience helps!