My 41' fiberglass sailboat has been a bit under-zinced since the get-go. I've thought about hanging a zinc guppy, but lately have been thinking about bolting on a hull zinc.

My boatyard endorses the use of an intermediate mounting plate such as Dry Zinc (http://www.fisheriessupply.com/productgroupdetail.aspx?cid=152125&keywords=divers+dream) for use with a zinc such as a Sea Shield Marine slotted zinc (http://www.fisheriessupply.com/productgroupdetail.aspx?cid=116128&keywords=divers+dream)

This system guarantees that over-tightening the mounting nut will not cause the thru-hull stud to twist. My problem with this is that it was really designed for transom mounting (not an option on our boat) and is really clunky for sticking in the flow of water past our beauteous hull. Dry Zinc - Sea Shield mounting system does get flow all around the zinc and the embedded galvanized mounts assure that it won't fall off due to zinc depletion around the studs.

The boat yard has suggested building up a fairing on the leading edge of the unit to keep from snagging stuff underneath and to smooth the water flow. The have offered to fabricate a plate for me at the same cost as the Dry Zinc.

Any suggestions?

In case you are wondering, my boat is not bonded. The prop/shaft assembly only has room for the prop's cone zinc. The stainless rudder shaft has shown some pitting and the rudder shaft log is supposedly aluminum. I'm planning to do limited bonding which would include the engine, prop shaft, rudder shaft and log all tied in to the hull zinc.

My preliminary tests show no stray current getting to the rudder assembly.