DIY Adding a Zinc Anode to a Wood-Cored Transom

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DaleH

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They say a picture is worth a thousands words … so I’ll be brief. Quite simply I remove the paint where I’ll affix a common ‘rudder’ zinc to my hull. For any anode type to work correctly, it must be in full contact with bare, clean metal. Tip – see the various charts online (or see below) for the best anode material to use for your boating use.

I drill a hole through the skin, but not all the way through the wood core. Let it dry out if needed. Then I wet-out the wood core with thin epoxy, once the thin stuff has ‘kicked’ (tacky, i.e., starting to cure), I imbed a SS threaded insert into the wood using thickened epoxy. Adding the thick to the curing 1st coat makes sure the 2 epoxy layers chemically bond with each other, which makes a stronger junction.

Then I just affix the rudder anode with a short SS bolt. Simple and it works! Just check the tightness of the bolt a few times during the season, as if/when the anode corrodes, it will get thinner. I use this trick on my aluminum hulls moored in a saltwater brackish estuary and I have zero corrosion complaints.

Also make sure to grease that bolt up well with a good waterproof synthetic grease. While all OB makers sell their own brand (typically a blue-colored one), they all come out of the same factory and the ‘best buy’ is the tub of Triple Guard grease from Bombardier or OMC (old stock). I can buy it for half the price of the import-branded motor stuff.

Anode Info from https://www.boatzincs.com/ Link = https://www.boatzincs.com/pdfs/Chart_B-Which_Anodes_Should_I_Use.pdf .

For vessels with (1) No AC Shore Connections; or 2) AC Shore Connections with Galvanic Isolation.
Aluminum hulls are susceptible to corrosion in all water types.

Freshwater:
Hull and Outdrives/Outboards – Use more active magnesium anodes (preferred) or aluminum anodes for self-cleaning performance.

Saltwater or Brackish Waters:
-In saltwater or brackish water (hull) use zinc or aluminum anodes.
-Outdrives and outboards with aluminum propellers should use zinc or aluminum anodes in salt and brackish waters.
- Stainless steel propellers on outdrives and outboards are galvanically incompatible with their aluminum housings and tend to inflict severe corrosion - use aluminum anodes (preferred) or zinc anodes.

Caution: Magnesium anodes should never be used on aluminum metal in salt water.

Exceptions: Outdrives with dual stainless steel propellers (e.g., Bravo 3) should only use aluminum anodes in salt and brackish water, and where possible, magnesium in freshwater.
 

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