Burned Ground wire?

2004 Merc 115 4 stroke....... found a burned ground wire coming out of the harness going to a block ground screw, wire insulation is burned but the actual wire is ok, just exposed, runs under and around the fuse block. Motor runs fine, can't see any other damage to wireing. Question is, should I go to the trouble to dig out the harness under all the fuse block and all the stuff there to run a bypass ground wire, or just not worry about it??? I know why it happened, previous owner crossed up a + and - on the battery one time. I've already fixed the damage under the dash, just found this today.

if the wire goes into any kind of harness etc where it is next to other wires i would cut and make sure you dont have exposure to a short to any other wire caused by burnt insulation.....then i would split some shrink tubing and place it around the wire and tape it well...assume they had that wire insulated for a reason.....

If you know the insulation damage was from the reverse polarity, then I'd get some double wall shrink tube and recover the wire...if you don't, corrosion will work its magic and then the starter won't want to spin the engine when you turn the crank...hard to say about the adjacent wires in the harness...would be good idea to inspect them...