I`ve always used a little heat from a heat gun to warm the decal so it is pliable and softens the adhesive. Now that worked great for all of the Starboard side graphics. However on the Port side all was going well with the front upper bow portion and the upper forward rear portion until about 1/2 way back, then it went crazy, coming off in little slivers. More heat made it worse as it would tear easily. I`m going to GUESS that this boat had more sun on this side in it`s lifetime to bake the decals.
The Port SeaDoo/Challenger 1800 decal was a nightmare the whole way thru and did not pull off like the other side did in sections...
so now it became a combination of glass cleaner, a razor blade making sweeps horizontally along bewteen the decal and the hull holding the razor blade flat against the hull as to not gouge the gelcoat. when the decals needed heat to assist and left that gooey adhesive, just take a hand full of ice from the freezer and rub over the decal glue for a bit, then take your blade and remove, make sure the hull stays wet, and it is a flat surface with no real contour changes. It took 2x longer to do the Port side... so you`ll need plenty of patience.:lols::facepalm:
I almost got all the starboard side graphics off in a few pulls, just keep you fingers close to the hull as you move along and don`t stretch the decals causing them to break, you then be able to get a good length off without trying to peal the edge up again...
I don`t have a direct answer bc some decals are easier/harder than others, especially ones that have been on for an eternity...