Pete,

Thanks for the corrected link Pete. I printed that .pdf file to read on the boat later today. The #10 wires from your chainplates probably served to ground your rigging to the original ground location. From the currently unconnected wire near your intake seacock, and from the comments made by Theis, that location appears to originally have been the fresh water thru-hull on the head intake.

As I recall, on my father's 35 foot cutter, the rig was grounded that way, but to zincs on the outside of the hull, and not to a thru hull. Grounding the rig should serve to slow crossion of the wire rigging, tangs, mast, boom etc.

My neighbor at the harbor recently had to replace the entire boom on her Coronado 25. When she removed the steel fittings on her aluminium boom, large corrosion holes were in evidence.The boom had to be replaced.