Zinc anode life, use of hanging zinc?

Ralph Johnstone · Nov 1, 2021

1) Yes, was in a bad marina for a spell and had to hang a zinc to be sure I didn't lose the shaft zinc completely before annual haul out.

3) Grounded ? ? ? You want to make sure there is a good electrical connection between the zinc plate and your shaft showing near 0 Ω on a multimeter. You may be able to do it by running a wire to your engine and get continuity to your shaft.

jssailem · Nov 1, 2021

It is like fishing for a solution without the proper equipment.

If you want to know your boats electrical potential and perhaps identify the cause, get a:
Corrosion Reference Electrode.

Corrosion Reference Electrode (CRE) with User's Guide

www.boatzincs.com

You can identify what on you boat maybe causing the zincs to disappear. Or you may be able to identify the culprit/culprits in you marina. At least in theory you could build a tool to find the electrical polluter.

NYSail · Nov 2, 2021

Also if it is the marina, a galvanic isolator is a fine upgrade.
Good luck

Greg

sail sfbay · Nov 2, 2021

Good advise above and would like to add..........make sure you have the correct anode for salt water What kind of zincs does your boat need? | West Marine. You might find this thread on strategies to extend anode life helpful: How long should a zinc anode last? | Sailboat Owners Forums

loneshark64 · Nov 3, 2021

On my new 343 the zinc is a tiny conical thing at the end of the prop. On my old boats I had one or two larger zincs on the shaft. I don’t know if it is the same on the 323 but it is a small amount of metal and no wonder that it wears out in half a season. There does not appear to be room on the shaft for one. I asked the marina guy to take a look at it this winter but he hasn’t yet. Anybody have a solution for this? would installing an isolator fix it? Seems like I would still need a larger zinc.

jssailem · Nov 3, 2021

loneshark64 said:
it is a small amount of metal and no wonder that it wears out in half a season

It is the statement "no wonder that it wears out in half a season" that seeks a solution. But the question really is: Why does it wear out in a season?

If there was no electrical charge to trigger the exchange of electrons, then the zinc would last a long time.

The "Corrosion Reference Electrode" will let you discover the cause of the electrical field on your boat. You can then decide if the zinc is doing it's job. You can use it to discover the electrical potential of the metals on your boat and and perhaps to identify if you do need more zinc to protect your boat.

Or guessing is also an option. Hang a fish, attach 3-4 zincs, or go bare.

loneshark64 · Nov 3, 2021

jssailem said:
It is the statement "no wonder that it wears out in half a season" that seeks a solution. But the question really is: Why does it wear out in a season?

If there was no electrical charge to trigger the exchange of electrons, then the zinc would last a long time.

The "Corrosion Reference Electrode" will let you discover the cause of the electrical field on your boat. You can then decide if the zinc is doing it's job. You can use it to discover the electrical potential of the metals on your boat and and perhaps to identify if you do need more zinc to protect your boat.

Or guessing is also an option. Hang a fish, attach 3-4 zincs, or go bare.

Yeah. OK. I’m sure you’re right. But I am an average boat owner not a metallurgical engineer. I don’t have these skills. I would not be able to be sure I am doing this procedure correctly. I would not be able to interpret the readings and know whether they are in range for the various metals involved. I wouldn’t be able to begin to figure out how to determine how to nail down how much of it is from marina stray currents or a hidden ground fault or any of that. Answers like this are basically zero help. For most people the question is what can I do myself, and when do I have to go to an expert? You are saying basically that I have to become an expert, and doing what most boat owners do, put a new zinc on every year, is “guessing” and stupid. Thanks.
Every boat I have had in our marina has had the zincs degrade over time. Other peoples boats too. So my simple understanding was that you replace the zincs each year to protect the boat and if you got the right one on there it would protect the boat all season. If getting it sized correctly is not the answer then I will hire an expert to figure it out.

loneshark64 · Nov 3, 2021

fullbore said:
The 323 supports the small prop anode (attaches aft of prop) and a shaft anode.
There’s only ~1” space on the shaft for that anode, but the shaft anode is fairly thick and probably has 2-3x more material than the prop anode.

I plan to add a hanging anode, with ~10x more weight than the other two anodes combined. Will also look into adding galvanic isolator.

Mine did not have a small prop anode when I bought it. I will try that. Thank you. Your answer was helpful. If that doesn’t work I will go get a frigging phd in electrical engineering like the other guy suggested.

jssailem · Nov 3, 2021

loneshark64 said:
I asked the marina guy to take a look at it this winter but he hasn’t yet. Anybody have a solution for this? would installing an isolator fix it? Seems like I would still need a larger zinc.

You asked. I qualify as Anybody.

loneshark64 said:
You are saying basically that I have to become an expert, and doing what most boat owners do, put a new zinc on every year, is “guessing” and stupid.

I did say without information about your boat, the replacing of zincs is guessing. I know because I did that. Yes it is done every day by many owners. It does not make it less guessing. Only that the guessing may have been successful if their boats prop/shaft are still usable.

I never would insult you by using the word "STUPID". That is not relevant, nor how I would talk to any boat owner.

NO you do not have to become an expert. If you want to be a more knowledgable boat owner that likes to DIY, then the suggestion was provided as an aid.

loneshark64 said:
But I am an average boat owner not a metallurgical engineer. I don’t have these skills.

This is a 3-4 skill level project for the average DIY boat owner. No special academic knowledge needed. Just the right piece of equipment and the guide to understanding the readings you see on the equipment. (provided in the package) If you can operate your cell phone or read a Digital Volt Meter you can identify the electric potential of your boat. From that, if the electrical charge that is eating your zincs is coming from your boat. Further if so, which of your systems may be causing the problem.

That leads to answering your second question... "would installing an isolator fix it?". No one can answer that unless they check your boat to see if your boat has a problem.

loneshark64 said:
I would not be able to interpret the readings and know whether they are in range for the various metals involved.

I do not have an advanced degree in Electrical nor Metallurgical Engineering. I can read the DVM and then compare the information to a chart which identifies metal being affected. If chart says it is zinc then there is Electrolysis corrosion occurring from my boat. For me that indicates I should be changing my zincs perhaps 3 times a year and looking for the cause. That may include getting a Marine Electrical Engineer (expert) to help.

loneshark64 said:
For most people the question is what can I do myself, and when do I have to go to an expert?

That is a question you have to resolve. If the information here is not helping for whatever reason, then seeking an expert makes a lot of sense, to me.

I hope you have a nice day.

Bluenose · Nov 5, 2021

Easy fellas"

MikeHoncho · Nov 6, 2021

loneshark64 said:
Yeah. OK. I’m sure you’re right. But I am an average boat owner not a metallurgical engineer. I don’t have these skills. I would not be able to be sure I am doing this procedure correctly. I would not be able to interpret the readings and know whether they are in range for the various metals involved. I wouldn’t be able to begin to figure out how to determine how to nail down how much of it is from marina stray currents or a hidden ground fault or any of that. Answers like this are basically zero help. For most people the question is what can I do myself, and when do I have to go to an expert? You are saying basically that I have to become an expert, and doing what most boat owners do, put a new zinc on every year, is “guessing” and stupid. Thanks.
Every boat I have had in our marina has had the zincs degrade over time. Other peoples boats too. So my simple understanding was that you replace the zincs each year to protect the boat and if you got the right one on there it would protect the boat all season. If getting it sized correctly is not the answer then I will hire an expert to figure it out.

Buy the electrode from that company. It comes with a fantastic manual that explains the physics and walks you through a proper troubleshooting algorithm . The book makes it a full package and eliminates the need for specific training. You will need a multi meter.

MikeHoncho · Nov 6, 2021

fullbore said:
I hung a 6-lb zinc anode from rear of boat today, reasonably close to prop anode. Should significantly prolong life of prop and shaft anodes.

Per the manual that comes with the test anode....it is just as bad to be over protected as it is to be under. It has to do with surface area so I guess if the zinc has a small surface area then It might be fine. What would be better is to figure out why you are burning through them

Ralph Johnstone · Nov 7, 2021

fullbore said:
Talking to other boat owners at the marina - seems that our rate of zinc consumption is normal.

OUCH ! ! !

Sounds as if the whole of your marina is under attack

. You're on the right track for the short term with a hanging zinc. As simple as what I mentioned in post #2. It's surface area which delivers the amperage and not weight of the zinc. Many years ago when I was in the poor man's marina, I used a 6 X 6 X 1/4" zinc plate and quickly slowed the wasting of the shaft zinc.

By way of explanation, I mentioned that I attached the wire to the engine block rather than directly to the shaft to avoid the embarrassment of accidentally turning the shaft and you can imagine the rest .....................