Re: outboard decals
If they are "stickers" like on most modern outboards, use a hair dryer to remove them and litttle if any adhesive will remain. Try goofoff for the rest, after experimenting in an inconspicuous place to be sure it doesn't damage the paint.
If they are truly real waterslide "decals", good luck, because you'll probably have to repaint the motor as well. Acetone takes them off.