Underwater Shaft Anode Replacement Video
- Thread starter fstbttms
- Start date
The friendliest place on the web for anyone who enjoys boating.
If you have answers, please help by responding to the unanswered posts.
If you have answers, please help by responding to the unanswered posts.
I'm using a hookah in the video. I would consider it unprofessional to do this work without surface supplied air. Or to do it while wearing a tank.
Capt.Bill11
Guru
Unprofessional to use a tank?
foggysail
Guru
If you bond your shafts using shaft brushes, shaft anodes can be eliminated. I made my own shaft brushes which work well. I verify my single (stern mounted aluminum diver's plate) anode's performance using my silver-silver chloride half cell.
Capt.Bill11
Guru
Most shafts are bonded with or without brushes.
Capt.Bill11
Guru
Neither apparently have all the bottom cleaners/prop changers that use tanks.
twistedtree
Guru
What sort of damage? Other than convenience, I wouldn't have thought the two approaches to be any different.
O C Diver
Guru
- Joined
- Dec 16, 2010
- Messages
- 12,865
- Location
- USA
- Vessel Name
- Slow Hand
- Vessel Make
- Cherubini Independence 45
While I use a hookah rig for the convenience of getting in and out of the water (no tank to take off), it also insures that I won't accidentally bang the tank against any part of my boat (including the prop) or my neighbors boat.
Ted
Ted
foggysail
Guru
I disagree. Shafts are coupled to transmission gears embedded in oil. There is no reliable bonding bonding there. It does not require many ohms to prevent electron flow when the galvanic voltage differences between metals is only millivolts.
foggysail
Guru
How do you place jumpers onto a rotating shaft? I can think of only one exception and that requires a thrust bearing.
Last edited:
We added a jumper on ours. Using 2 ring lugs that fit the coupler bolts and ~3" of #10 wire. We jumper across the coupler on the same bolt. Our shaft is 2" diameter that spins at ~800-900 rpms. The shaft runs true and the alignment is good.
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.
foggysail
Guru
A picture might help. I cannot vision a jumper of any material connected to a rotating shaft. Of course, something could "rest" on top of such a shaft similar to what I call a shaft brush. My stuffing box is bonded but that doesn't by itself make an electrical contact to the shaft.
My first attempt to bond my rotating shafts used a bronze bar that rested on the shaft. It failed due to rapid wear. Today I use sintered oil impregnated bronze to make the shaft contact.
psneeld
Guru
foggysail
Guru
foggysail
Guru
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.
C lectric
Guru
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.
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.
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???
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???
Capt.Bill11
Guru
"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."
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."
psneeld
Guru
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.
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.
Last edited:
Lou_tribal
Guru
As a diver you should now that your tank does not have to be on your back... Ever heard about sidemount?
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.
