Edd, What would you be using the fish for that you would be trying to help with? By what metric would you know if they helped? Would you be able to prove that it was or wasn't helping and determine why or why not?
Most of the above questions *could* be answered if you had a galvanic cell and meter and knew how to use them. For steel or aluminum boats this is a critical tool for determining if sufficient anode protection exists or remains. For fiberglass boats its probably not worth your time or money. Generally shaft and engine zincs are installed /recommended by the manufacturer to prevent 2 DISSIMILAR metals from experiencing GALVANIC corrosion. Notice that I didn't say "prevent a single metal from simply corroding"? Attaching a zinc to a carbon steel plate in or out of the water will accomplish nothing. The steel plate will still rust and at the same rate regardless of the zinc. If the OEM zincs are being consumed too quickly then a problem *may* exist. First, if you are not connected to shore power then you can eliminate it being a problem with other people's boats or the dock wiring. Second, you may need to consider the duration of the service interval. Talk to others regarding their service interval to get a feel for what they experience. Third, you may have a zinc that is too reactive for your waters OR for the material that you are trying to protect. We call them zinc but in reality they can be made from aluminum, magnesium, OR zinc. Boatzinc.com gives good guidance in this regard. Fourth, you may need or want to increase the size of the zinc to provide more material. If you find that the service interval is long or that the zinc seems to *not* be being "eaten" then it could be that the zinc isn't making good electrical contact. IMO this is actually the worst case scenario since you have a false sense of security that your metal is protected. So, IMO, the fish are at best a waste of money and at worst masking a problem. For my 37+ and maybe for yours too Edd there just aren't many underwater metals that need protecting. All my through-hulls are Marlon (plastic). The engine didn't come with zincs (evidently the OEM doesn't recognize a galvanic corrosion risk). Which leaves the shaft and the prop. A cone on the prop and a clamp-on on the shaft. I've tried more than one shaft zinc and oversized zincs just for kicks. At the end of the year there is just more anode to throw away. Doubling up or oversized would be my solution if a service interval longer than a year were desired. Josh Muckley S/V Sea Hawk 1989 C&C 37+ Solomons, MD On Tue, Jul 9, 2019, 9:58 AM Edd Schillay via CnC-List < [email protected]> wrote: > Listers, > > Every once in a while, I come across a boat with a submerged zinc hanging > from a wire off the stern of a boat. Some people swear by them and others > think it’s a wasted effort. > > What does the group think? Is it worthwhile to add (especially when on > shore power) and, if so, where do you connect it on the boat? > > All the best, > > Edd > > > Edd M. Schillay > Captain of the Starship Enterprise > C&C 37+ | Sail No: NCC-1701-B > Venice Yacht Club | Venice, FL > > Starship Enterprise's Captain's Log <http://enterpriseb.blogspot.com/> > > > > > > > > > > > _______________________________________________ > > Thanks everyone for supporting this list with your contributions. Each > and every one is greatly appreciated. If you want to support the list - > use PayPal to send contribution -- https://www.paypal.me/stumurray > >
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