If it was mine... and it was small areas that were cracked... I'd paint over it with brush on electrical tape or tire bead sealer. It's the same product. Paint that on for a seal. Then tape over it to strengthen the remaining insulation. Then paint sealer on again to keep moisture out.
If the entire cable is bad/cracked... just replace it with like cable from a welding supply store. 2/0 cable is something like 3 bucks a foot.