A sharp knife such as an # 11 X-acto blade can be used to cut carefully around all of the sealant. Cut with the sharp edge toward the fiberglass, and rotate it around the wire. Good chance that sealant is just near the outside, and once you get it cut, you can pull the internal wires out thru the holes in the transom. I have some small wood carving gouges I use for this--about 3/16 diameter gouge works well for this. But the #11 blade is fine.
Be sure and check out the wires under the splash well first. Then you can loosen them up to the point that they will not cause resistance to being pulled out thru the transom. There should be plenty of slack, if not, then undo the connectors, and that should give you plenty of wire to work with.