It looked like the original winch mounting had pulled through the bridgedeck at some point. Repairs had been made over the years, involving a mild steel bar, now very badly rusted, and sections of 2x4, visible in front of the winch. I found two pine grubs happily munching away inside the posts... you can see the extent of the rot on the bottom. The plan is to fabricate a custom bracket out of stainless. I believe the winch itself can be cleaned and salvaged, since the rust is mostly on the surface.