Excessive zinc relacement

Don S/V ILLusion · Sep 10, 2016

That is a knot meter. The cap is used to close the thruhull when it is removed for cleaning (as it is now).

Before getting too wrapped up in the myriad of possible reasons for zinc loss, the first question is whether you can tell if the zincs are being eaten away that quickly or do you have an over-zealous hull cleaner prone to exaggeration. Have you seen the zincs he removed from your boat?

rardiH36 · Sep 10, 2016

As a 80% live aboard, you probably encounter lots of owners in the marina. Ask them about their anode depletion experiences and solutions. That should help you zero in on whether you've got "hot" location issue, or maybe also have some fault with your boat. Either case, a pro can assist zeroing in. Probably a better alternative than moving marinas only to find the same issue elsewhere.

Since you spend lots of time on your boat almost every day, unplugging from shore power say during the day, but connecting again every night, might slow the replacement frequency down a bit, but it's not the solution.

A stop-gap option, particularly since you don't leave the berth much is to hang a "fish" zinc.

On my boat, I have a shaft zinc, but I also have a "fish" zinc hanging over the side. It does sacrifice, so that's evidence it is helping. Between the two, the shaft zinc depletion rate is definitely reduced. If I didn't ever sail, I might even forgo maintaining a shaft zinc. But on the other hand, props are expensive, so its not worth saving a few zinc $'s in the exchange.

To ensure a good contact between the fish zinc and the shaft, I installed a shaft brush like this: http://shop.sailboatowners.com/prod.php?5673 to which the hanging fish is connected to. And for good measure, I also have run a "pig tail" from the fish lead to the engine block.

As to the fish zinc, the sailboat marketed ones are expensive. So I have a supply of these $3.60 zincs which are marketed to crab/lobster fishermen to protect their pots: https://rotometals.com/1-5-lb-tie-on-crab-pot-zinc-anodes/. To use these you will have to design your own connection between the crab zinc and the wire leading to the shaft brush and engine block. But if you design right, its a simple matter of pulling up the fish zinc every few weeks and if it is pitted/sacrificed, fit on a new one.

Don S/V ILLusion · Sep 10, 2016

I once did what Randi suggested and found it did work as a temp fix.
Simply run an unbroken wire connected directly to the shaft into the water with a zinc attached. As you don't move, there is no concern for forgetting to disconnect it from the shaft. Being unbroken is important to minimize any resistance along the path.

JamesG161 · Sep 10, 2016

FriscoRon said:
I was told I'm in a hot spot marina

You should move immediately or have them find the "hot spot" culprit. I had to find the "bad actor" in my marina.
Once he fixed his newly wired boat. I change my zincs once a year.
Jim...

fstbttms · Sep 11, 2016

FriscoRon said:
I was told I'm in a hot spot marina.

I have been told by boat owners in virtually every one of the dozens of marinas I have worked in over the last 22 years that their marina is "hot." Usually this is not the case and is the result of the boat owner simply being in denial about the state of his own electrical system. Rapid anode depletion is almost always the result of an electrical issue aboard the boat in question. Cudos to you for acknowledging that possibility.

The anode loss you appear to be experiencing is extreme. I would recommend you do two things:

1.- Have a marine electrician go through your electrical system to suss out the problem. If he can't find one aboard, have him check the shorepower system and for any stray current in the water. If there is an issue with either of these last two items, request that the marina alleviate the issue.

2.- Require the dive service to leave all anode remnants on the dock each and every time they replace one. It is a little suspicious that they have "forgotten" to leave the majority of the anodes they are replacing, especially since they are replacing them so frequently. They should be concerned with providing you with evidence of the problem. If they seem to be unable to do this, find another dive service.

BTW- the rudderplate anode is mounted on your strut, not on your rudder.

rardiH36 · Sep 12, 2016

FriscoRon said:
Thanks Rardi,
I was told I'm in a hot spot marina. I'm little confused on the rigging of this fish zinc and shaft brush. Is there anyway you can provide me with a diagram or photo of this rigging.

Ron

Ron:

Being at my boat yesterday, I took the attached picture of how I have connected the hanging zinc to the SS wire (salvaged from an old lifeline!) that leads up to my boat. The same clamps and wire have been in the water now for 3-4 years.

Inside my cockpit, I have installed a connector plug, so when I go out sailing, the hanging zinc wire can be easily detached from the further "interior" wiring for the run to my engine block and shaft brush. I tie the hanging zinc to a small line on the dock so I can quickly re-attach when I return.

As to more details, although I am comfortable that my hanging zinc bonded to both the engine block and the shaft brush assists with my protection*, I am not expert enough to confidently commit to any specific details.

Lots of info is available on the net: Search for Hanging Zinc Anode. And Marine Shaft Brush.

As mentioned my opening post. A hanging anode is something that is easily added to assist, but not solve your problem. So certainly follow-up on the other suggestions.

* For instance, just last week, I engaged a diving service to clean/inspect my bottom and check (and replace if needed) the shaft zinc. At the last service, about 4 months ago, the diver reported that the already 6 month in-service shaft zinc was still fine until the next service. But at last week's cleaning, the zinc was gone. Fallen off at some point. So I had the comfort knowing that the hanging zinc at some point assisted assuming the protection duty. Also attached is a picture of a new anode vs one that had been in the water for I think about 6 months. The difference shows the hanging zincs are sacrificing. At the time of the photo, I was using Aluminum Alloy anodes. I have since gone back to zinc.

Charles Erwin · Sep 12, 2016

Fast is right. Stop guessing and listening to rumor. Measure your hull potential and in less than 10 minutes you will find the answer

Charles

Charles Erwin · Sep 13, 2016

Yes any VOM will do but your article discusses AC and AC will have nearly nothing to do with zinc wasting.

Get 20 feet of no. 16 wire and solder a pencil zinc to the end. The VOM probe goes to the shaft, pencil zinc wire to VOM common, with pencil zinc in the water.

Test for DC volts with VOM on low scale. Same test for any other under water metal with zinc.

I will send you a sketch when I get off boat

Charles

Barryr8195 · Sep 22, 2016

Check the galvanic isolator. It should be installed where the shore power enters the boat.

Chief RA · Sep 22, 2016

It was suggested that your diver may be replacing too often. While it appears you may have a problem, I would not personally replace a zinc in as good a condition as your picture shows. Fstbttms can probably advise more on this. Chief

SOCAL C50 · Sep 24, 2016

I am in LA harbor (Wilmington), which marina are you in?

fstbttms · Sep 24, 2016

Chief RA said:
I would not personally replace a zinc in as good a condition as your picture shows. Fstbttms can probably advise more on this. Chief

The pic does not adequately show the state of depletion of the anodes, IMHO. Tough to make a call based on that.

Ken Cross · Sep 25, 2016

My zincs looked pretty good on this haul out until they got hit with a pressure washer. I could see that were clearly wasted. I'm just curious why one would switch back to Zinc from aluminum? I too need to spend a couple minutes checking my Galvanic Isolator.

Ken

Chief RA · Sep 25, 2016

Ken: you need a sacrificial metal which means the least noble. This means the softest metal will corrode first. Zinc is usually used and seldom aluminum. You might use aluminum if you know you have NO aluminum such as a prop in the water.
Chief

MitchM · Sep 25, 2016

check whether anyone close by in your marina has a Carver which was recently re wired by an amateur non - ABYC certified electrician.

Excessive zinc relacement

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SBO Weather and Forecasting Forum Jim & John

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