Question for the Mercury outboard guys

If its what i think your talking about i would assume it is a ground or what we call on our aircraft a static wick to discharge any build of of static electricity, between the lower unit and the main motor housing when running. I know in the rotorcraft (helicopter) world having a fast spinning rotor head when completing hover operations ove rthe water the static eletricity that builds between the aircraft and the water can cause some electrical sparks when lowering our rescue basket down to the water or to a vsl, which is why the boat crews will ground the basket or rescue swimmer with a deadmans stick prior to touching it/them. I would assume your prop spinning through the water is producing the same electrical field and that wire is your ground between the lower unit and the sensitve electrical systems found on todays outboards. Id get it repaired or replaced.