"If Todd does not know what this cable is used for then it is extra."
Todd here.
I liked the one about the lobster traps.
Did you ask the previous owner? I hope it's not really there for a reason of boat stability.
As others have also posted, it's not something that comes with the boat, or even a common add-on.
My vote is ask who put it there.
Todd Bouton
n6.0na
+sq top and spin/snuffer
#111