you might try using lighter fluid or a product called energine cleaning fluid on a rag...I would try it out on a sample first thou, just to make sure...it shouldnt hurt the ABS. ...Then wash with soap and water to remove any fluid residue....I would do this on a a boat i currently have to verify for you, that im peeling off the decals to use on my display boat, but I dont have either product around here right now........if I recall correctly, I cleaned up an older bud light ABS boat using this method that I display and it didnt even hurt the original decals, but it cleaned up the boat beautifully.....and a little elbow grease using the rag....but this should do the trick for you.....mike