Underwater Shaft Anode Replacement Video

Lou_tribal said:

As a diver you should now that your tank does not have to be on your back... Ever heard about sidemount?

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I'm not a recreational diver and have no need for a recreational diver's toys. Why would I wear a tank in the water? Regardless of how you have this 30-pound metal cylinder hanging off your body, it's going to hinder movement, restrict access to tools, require a BCD and make it hard to get in and out of the water. Plus, tanks have to be refilled whereas a hookah is unlimited free air. In most cases in this business, using them makes little sense.

Wearing a tank to clean boat bottoms is like wearing clown shoes to the office. Yes, you will get the work done but you are going to look silly doing it.

psneeld said:

If properly done and maintained, shaft brushes usually work as sdvertised. They don't need to be fancy or complicsted, and have been suggested for as long as I have been boating by experts in my readings.

They aren't common, but I have used them on 2 liveaboards.

Brushes have the advantage that if the shaft zincs deteriorate to the point they are loosing their protection from mass loss or corrosion getting under them and the transom zincs are starting to also, the transom zincs are more easily replaced (especially in the NE winters).

They also keep working if you are on a cruise and you shaft zinc falls off (and they do occasionally). Tough to monitor unless you swim a lot or check eery day with a camera. I eyeball my transom zinc most days when I check the exhaust for water fliw, color, and smell.

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Well stated


I changed my approach to anodes 10 years or so ago. Too many zincs and questioned why. So I purchased a silver-silver chloride half cell and applied my engineering background to find a different approach to anode problems. I believed that only one anode would suffice but it would need to be both large and properly located. Also I needed to resolve the shaft problem.

Aluminum seemed to answer my size issue with its higher ampere hour capacity over that of zinc. Next I made my own shaft brushes which took two attempts before I had something reliable. My choice for anode was an aluminum diver's plate, 1/2"X6"X12" and sure enough, all my exposed metals were in the -0.75v range as measured with my half bridge.

Later I found that my diver's plate could only provide protection for a little over 3-4 months. So I increased its thickness from 1/2" to 1" which works out well.

I have even thought about building an ICCP (impressed current cathodic protection) system. At the moment though, I have enough to do without taking on another challenge although I believe it's just a matter of time before I build one.

fstbttms said:

Electric Shock Drowning (ESD) is almost exclusively a freshwater phenomena. It is very rare (if indeed, it happens at all) in saltwater. I have been diving in saltwater marinas for 22 years and have never even felt a buzz.

That said, I have heard anecdotally of divers who have. No deaths or injuries, but I do unplug every boat I work on as a precaution.

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Thanks, FB - I'm always learning!

ESD Explained - By Beth Leonard - What every boater needs to know about Electric Shock Drowning.

Electric Shock Drowning (ESD) Explained - Seaworthy Magazine - BoatUS