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Old 11-12-2016, 10:05 AM   #21
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Hmm, wonder how the brush out of an electric motor would work. The last 4"grinder I worked on had brushes with a wire attached.

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Old 11-12-2016, 10:08 AM   #22
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Like this........ from Nigel Calder's book.....

For my brush, I use a discarded out drive zinc...already has a bolt for the bonding wire and arm attached. Got 3 seasons from the last and free from the marina pile is hard to beat.


YES! Your brush (if bonded) looks adequate to bond your shaft!!!
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Old 11-12-2016, 10:25 AM   #23
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I would take pictures of mine but the boat is shrink wrapped. I used two brass bars about 15" and secured 1/2 of a cut oilite bearing to the ends that ride on the shafts. The other ends I soldered a brass door hinge which I bolted to a stringer. The weight of the bar assembly rests on the shaft itself. It was as simple as I could make them. No springs needed.
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Old 11-12-2016, 03:29 PM   #24
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I used one of these years ago. Just need to check it that there is continuity between the shaft/brush contact and then to the bonding system.

I periodially clean the area of the shaft that the brush rides on.

This unit actually uses a motor brush soldered to the brass bar.

PROFESSIONAL MARINER Shaft Brush | West Marine

There are other ways of doing it. I have seen shafts bonded with a piece of brass half pipe. These were on slower shafts like many trawlers.
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Old 11-12-2016, 05:15 PM   #25
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I'm surely no professional in-water service tech. However, having good breath-hold capacity I do my own under boat service while boat's in the water. Although a limited time for each breath-hold sequence... nothing in my way while working. I count accomplishing these things as part of my boat owning enjoyment.

BTW: I do this while at anchor and not while at dock for fear of stray AC currents that might kill.

I often wonder if bottom cleaners who work around docks ever run into too severe AC currents in water???
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Old 11-12-2016, 07:34 PM   #26
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"So, what is this all about anyhow? The concept here centers around bonding of the shaft to the hull for the purpose of mitigating corrosion. The idea is that propeller shafts really don't make a very good electrical connection to the rest of a boat's bonding / cathodic protection system since the propeller shaft is connected directly to the transmission (reverse gear) at the back of the engine. Electrical continuity through the transmission is always a bit dicey, especially when underway.

So, how do these shaft brushes do in this situation? Usually not too well frankly. Most of us that deal with matters of marine corrosion don't actually recommend them. The failure rate for these brushes, and especially something as jury rigged as the one in the photo above is just too high. I've checked many of these over the years for electrical continuity and found an open circuit between the shaft and the brush.

So, what's the answer here? Simply provide adequate shaft anodes to protect the shaft and propeller for a reasonable amount of service time and treat any other underwater metal you wish to protect separately with additional anodes as needed. Most of these shaft brushes are just going for a ride on the boat they're installed on and really not contributing much to help in the corrosion protection area."
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Old 11-12-2016, 09:12 PM   #27
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I believe in and rely on anodes attached directly to underwater metal gear.
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Old 11-13-2016, 06:16 AM   #28
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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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Old 11-13-2016, 08:47 AM   #29
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Quote:
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As OC mentioned, it is very easy to imagine a diver with a bulky tank on his back banging up a boat's anti fouling paint or even gouging the gel coat.

From a personal standpoint, when I see a hull cleaner in the water or on the dock with a tank on his back (which is not often), I assume he doesn't know what he's doing. In any event, I do not allow my divers to operate that way.
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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Old 11-13-2016, 08:54 AM   #30
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BTW: I do this while at anchor and not while at dock for fear of stray AC currents that might kill.

I often wonder if bottom cleaners who work around docks ever run into too severe AC currents in water???
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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Old 11-13-2016, 09:04 AM   #31
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As a diver you should now that your tank does not have to be on your back... Ever heard about sidemount?
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.
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Old 11-13-2016, 09:38 AM   #32
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Quote:
Originally Posted by psneeld View Post
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.

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.
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Old 11-13-2016, 10:47 AM   #33
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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.
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
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