Re: Removing painted letters
If the paint has been there for a long period of time the gel coat around it will have oxidized and flaked away at the microscopic level.
What that means is you'll have a 2 millimeter or less 'bump' where the letters where that believe it or not will be visible.
Wet sanding with a long board is the only way to kill it/smooth it off.
Lessons learned are opportunities earned.