How many anodes on your prop shafts?

Carpediem44DB

Carpediem44DB

Well-Known Member
Aug 18, 2015
3,230
Sanfransico Bay area
Boat Info
2000 Carver 506
2006 44 DB Sedan Bridge
Engines
Volvo TAMD 74 P
We have the boat we are buying out of the water for survey and bottom paint and anode replacement. We are in brackish water so going with Aluminum. The shafts are 2 1/4 inch and currently have three zincs on each shaft. Its a 51 foot boat with 31 inch props. You guys with the 500s and 560s, how many anodes do you have installed? I understand that Searay did not even install anodes from the factory. The boat does have the same Isolation transformer that was on the Sea Ray shore power circuit.
Thanks
 
I removed mine from the shafts as Searay does not use them. Never any issues.
 
Does the boat have brushes on the shaft that connect to the green bonding system in the boat? If it does the zincs shouldn't be needed.
 
hottoddie said:
Does the boat have brushes on the shaft that connect to the green bonding system in the boat? If it does the zincs shouldn't be needed.
Click to expand...

mine is only a 30’ but mine is the same as above. Also when I did have them I kept throwing them, last time they hit the prop and one of them had to be sent off to be retuned
 
3 zincs per shaft seems kinda excessive. My last boat also had zero shaft zincs in lieu of a bonding brush near the coupler in the engine space. That ties back to the hull plate on the stern.

After the first season, however, I thought the hull zinc was wearing pretty fast. Next season I changed it from zinc to aluminum. I also changed the rudder and tab zincs to aluminum and upsized the one on the rudder.

Just as another example of why a bonded prop shaft can be better than a collar anode, during the survey on my current boat a diver found the shaft zinc had slipped and was jammed against the strut. He freed it up and there was no damage but it could certainly have been a problem. I wondered why the boat even had a shaft zincs because Back Cove doesn’t install them at the factory. Later in the survey I found the factory-installed shaft bonding brush was broken.

Edit: I boat in salt water.
 
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Read this @Mig22

b_arrington said:
3 zincs per shaft seems kinda excessive. My last boat also had zero shaft zincs in lieu of a bonding brush near the coupler in the engine space. That ties back to the hull plate on the stern.

After the first season, however, I thought the hull zinc was wearing pretty fast. Next season I changed it from zinc to aluminum. I also changed the rudder and tab zincs to aluminum and upsized the one on the rudder.

Just as another example of why a bonded prop can be better than a collar anode, during the survey on my current boat a diver found the shaft zinc had slipped and was jammed against the strut. He freed it up and there was damage but it could certainly have been a problem. I wondered why the boat even had a shaft zincs because Back Cove doesn’t install them at the factory. Later in the survey I found the factory-installed shaft bonding brush was broken.
Click to expand...
 
PO had 2 on each shaft. There was always a lot of material left on the two. I switched to just one. No problems, minimal “wear” but I feel still needed.
 
Thanks Guys, The Owner kept the boat in SF as a condo and only had the bottom cleaned semi annually so I think that is why they had the extra anodes. They were at about 50% in 7 months and the running gear shows no signs of unusual corrosion so I think its a little over kill. I think Ill look into installing prop bonding brushes and go sans anode, one less thing to worry about under the water. Ill see if I can get any response over at the Carver forum, as I mentioned before, they are not nearly as active with technical information sharing for some reason.
Cheers
 
I installed one on each shaft of my boat on the last haul out, thinking of it as an insurance policy. If all else failed, I had some protection. I was also aware that these things can and do come loose.

One thing to consider is you can have the boat "over anodized". According to this article from Practical Sailor, "Typically, you want a sacrificial zinc that has about about 1 to 2 percent the surface of the metal it is protecting". --> https://www.practical-sailor.com/blog/can-you-have-too-many-zincs.

I've never seen a formula or rule of thumb on this, so this was an interesting read for me.
 
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dtfeld said:
I installed on on my boat on the last haul out, thinking of it as an insurance policy. If all else failed, I had some protection. I was also aware that these things can and do come loose.

One thing to consider is you can have the boat "over anodized". According to this article from Practical Sailor, "Typically, you want a sacrificial zinc that has about about 1 to 2 percent the surface of the metal it is protecting". --> https://www.practical-sailor.com/blog/can-you-have-too-many-zincs.

I've never seen a formula or rule of thumb on this, so this was an interesting read for me.
Click to expand...

Maybe I should clarify that when I changed the rudder anode I went from a standard to “heavy” version. Same diameter, but thicker so it lasts longer.
 
hottoddie said:
Does the boat have brushes on the shaft that connect to the green bonding system in the boat? If it does the zincs shouldn't be needed.
Click to expand...
I have always wanted to see the "brush system". Seems like a much better idea then having zincs on a shft that is spinning. I have had to dive and remove shaft zincs because they came loose and started banging on the cutlass in the middle of a trip to the Bahamas twice now.. I hate those things. If anyone knows of a brush system please post about it....I want one
 
ocgrant said:
I have always wanted to see the "brush system". Seems like a much better idea then having zincs on a shft that is spinning. I have had to dive and remove shaft zincs because they came loose and started banging on the cutlass in the middle of a trip to the Bahamas twice now.. I hate those things. If anyone knows of a brush system please post about it....I want one
Click to expand...
This one was posted over on Yacht Forum in a post about shaft seal longevity. I hope to have my ER looking like this one soon!
20190317_122249-jpg.84303
 
This is the one that was in my boat. The copper strip acts as a spring to hold the brush on the shaft. It’s a carbon/graphite block welded to the end. The bonding wire connects back the rest of the bonding system.

upload_2021-1-24_11-8-46.jpeg
 
Those look like the ones in my boat. I added them 6-7 years ago when I installed "drive saver" couplers. The drive savers isolate the shafts from the transmission therefore the need for the bonding brushes.
 
Is there a kit out there someone can buy?
 
ocgrant said:
Is there a kit out there someone can buy?
Click to expand...

I picked up my grounding brushes from the prop shop when my props were being reconditioned. I think they were only about $30 per side but the was 7-8 years ago.
 
Slight change of plans, I am going to build a bonding system, Install one aluminum anode on each shaft and have the diver take it off at the first cleaning in three months so I can see the rate it is wearing and decide then whether or not to run more than one anode going forward.
Thanks for the experience and advice.
Carpe Diem
 
My Tiara uses 1 zinc per shaft. Yes you can over zinc. The only way to truly tell what you need is have an electrician test the bonding system in your slip after the boat has sat for a day or two. Based on those reading you will be able to tell what you need. At least that is the way I understand it and what I did. Works well for me and change the zinc about every 6 months.
 
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