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Old 06-02-2020, 10:52   #16
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Re: Hanging zinc what am I missing

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Originally Posted by bobgarrett View Post
Volvo saildrives are insulated from the engine to reduce electrolysis.
We weren't discussing saildrives. Apples and oranges.
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Old 06-02-2020, 11:16   #17
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Re: Hanging zinc what am I missing

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Originally Posted by arch007 View Post
I am wondering why I need zinc on the propellar if I use a
Hanging zinc attached to the prop shaft.

What am I missing ?

Why do I need a prop zinc. I spend 95 per of the time in a marina.
Replacing a prop is expensive, and if it is a feathering prop, involves multiple boat bucks.

Being in a marina 95% of the time is about as bad an environment as you can have for electrolysis. Zincs donít dissolve from abrasion - they respond to the flow of electricity, whether caused by galvanic action between dissimilar metals, or from stray currents in the water your boat is flowing in.

Skimping on zincs is a classic example of penny-wise, but pound foolish.
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Old 06-02-2020, 11:41   #18
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Re: Hanging zinc what am I missing

Our prop is a feathering 3 blade. Itís expensive and takes an expensive nose cone anode. Every time Iím tempted to do away with the nose cone and use only the shaft anodes I lookup the replacement cost of the prop.

I think Iíll order another few anodes from Oz while Iím thinking about it.
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Old 06-02-2020, 12:12   #19
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Re: Hanging zinc what am I missing

I nearly certain that on an Amel the entire engine and sail drive are isolated.
I was looking at a friends and noticed a relay for the negative wire, it seems when the engine is off, it’s disconnected from the vessels ground system.

My guess is this is to prevent stray current from eating the saildrive like you see on other vessels.

I had never thought about the rubber bushing on the prop isolating, but yes it seems all outboards made in the recent past also have their props isolated.
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Old 06-02-2020, 13:35   #20
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Re: Hanging zinc what am I missing

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Originally Posted by fstbttms View Post
We weren't discussing saildrives. Apples and oranges.
When you criticise a post you should not take a sentence out of context just to show you did not know about Volvo props.
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Old 06-02-2020, 13:57   #21
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Re: Hanging zinc what am I missing

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We weren't discussing saildrives. Apples and oranges.
I think the civil response is something on the lines of "Thanks, I learned something new I didn't know before today."
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Old 06-02-2020, 15:11   #22
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Re: Hanging zinc what am I missing

Thanks to everyone for their help.

Learnt a lot !
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Old 06-02-2020, 15:50   #23
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Re: Hanging zinc what am I missing

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Originally Posted by a64pilot View Post
You shouldnít, but if itís wasting away, thatís telling me you do. My guess would be that your hanging zinc isnít connected well to the shaft.
However stainless steel is a poor conductor, but it seems all hanging zincs cables are made from SS?
It would seem that a hanging zinc is at a disadvantage right from the beginning.

I have a battery I use for my hookah gear that has SS terminals.
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Old 06-02-2020, 17:11   #24
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Re: Hanging zinc what am I missing

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Originally Posted by a64pilot View Post
A prop zinc is just too easy, and not expensive.
Crazy not to have one, running gear is just too expensive to not protect.
This^^^
Price up a new prop or prop shaft, and the labor to install that stuff, then look at the price of a collar zinc. That should pretty much end the conversation I would think.

Fair winds,
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Old 06-02-2020, 18:04   #25
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Re: Hanging zinc what am I missing

A couple of thoughts in summary of what has already been said, mostly

1. I have generally found marina's to be the worst environment for electrolysis, so that is where one really needs to pay attention.

2. Yes, shaft and prop zincs are well worth the cost and effort.

3. I also hang a spare zinc overboard in marinas as an early warning device. If it shows unusual erosion it's time to check the boat's zincs.
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Old 06-02-2020, 18:18   #26
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Re: Hanging zinc what am I missing

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Originally Posted by Pegu Club View Post
This^^^
Price up a new prop or prop shaft, and the labor to install that stuff, then look at the price of a collar zinc. That should pretty much end the conversation I would think.

Fair winds,

My prop has about 1/2" of shaft exposed, too slim to put any collar zinc on. Currently I have a zinc attached to the hull connected to the shaft via a brush inside. Is it possible to add a prop-nut zinc onto a set-up like this?
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Old 06-02-2020, 18:20   #27
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Re: Hanging zinc what am I missing

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Originally Posted by Ramona View Post
I have a battery I use for my hookah gear that has SS terminals.
You may, but that doesnít make it a good conductor.

https://www.tibtech.com/conductivite.php?lang=en_US
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Old 06-02-2020, 18:23   #28
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Re: Hanging zinc what am I missing

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Originally Posted by Kelkara View Post
My prop has about 1/2" of shaft exposed, too slim to put any collar zinc on. Currently I have a zinc attached to the hull connected to the shaft via a brush inside. Is it possible to add a prop-nut zinc onto a set-up like this?

Yes you can fit a prop nut zinc. Real easy replace and widely available. Off topic but have switched to aluminum anodes as Iím sometimes in brackish water, and I prefer them over zinc even in salt water.

https://www.boatzincs.com/propeller-...nc-anodes.html
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Old 06-02-2020, 18:24   #29
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Re: Hanging zinc what am I missing

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Originally Posted by a64pilot View Post
Yes you can fit a prop nut zinc. Real easy replace and widely available. Off topic but have switched to aluminum anodes as Iím sometimes in brackish water, and I prefer them over zinc even in salt water.

https://www.boatzincs.com/propeller-...nc-anodes.html

Excellent! so as long as I make sure I get the correct thread size I should be able to just replace the current nut?
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Old 08-02-2020, 05:38   #30
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Re: Hanging zinc what am I missing

I usually do the same as Jammhass. Shaft anode, prop anode and an extra anode over the side if the boat is not going to be moved for a while. The large one over the side is of course on an SS wire and is about 2m (6ft) away from the prop so i am not convinced it is really effective but i do it anyway.

Would i do away with the prop anode? No, because i find that after about 12 months it seems to have been the prop anode doing a lot of the protection and is the one that is most consumed. Since i have space i now install 2 shaft anodes close to the prop as well as the prop anode.This maybe overkill since neither of the two shaft anodes is down to 50% after 12 mths meanwhile the prop anode is always down to about 50% or sometimes 25%

Yes, i hv a feathering prop and most certainly will do whatever is nec to protect an expensive piece of equipment. Who cares if the anodes are only 10% consumed? In Europe they cost about Ä20 ($25) each so are a bargain compared to the cost of a new feathering prop.
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