I just purchased a used fiberglass boat that the tag registration decals have been painted on. The decal will have to be changed because the boat changed states. Not sure what kind of paint was used. What would be the beat way to remove without damaging the gel coat? 

I found this by doing a search I don't have any experience using this product https://www.owatrolusa.com/product/marine-strip/

Acetone should remove the paint. 

Painted on, that is interesting.  In Virgina you get a new registration decal every two years and place it on the bow right below the rub rail. The expiration year is in big numbers and the color changes with each new issue.

8 minutes ago, OnthePotomac said:

Painted on, that is interesting.  In Virgina you get a new registration decal every two years and place it on the bow right below the rub rail. The expiration year is in big numbers and the color changes with each new issue.

I think he's talking the registration number.

Look at my canoe - reg number is done with vinyl decals while the state tag is a sticker. Our registration is on a three-year cycle. Quite a few people here paint their reg number on the boat.

Aha, we call it  hull number.