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Old 11-07-2014, 09:45 AM   #1
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Zincs

I plan on doing 1/2 the loop in 2016 or 2017. I will take my boat from Long Island NY to Florida. I think it's a state law in NY. "When you retire, you move to Florida."

Anyway, my question is about zincs. The trip I am currently planning brings me from salt water into fresh water and back again. I use zincs now. I heard in fresh water people use aluminum vs. zincs. I also heard once zincs hit fresh water they get a film over the top surface and stop working until you scrub off that coating. Does anyone have experience with traveling thru salt water and then fresh water and back again?
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Old 11-07-2014, 10:20 AM   #2
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Actually, as I recall, aluminum can work in both salt and fresh water. Perhaps not ideal in either compaired to zinc and magnesium. But I would just change them out to zinc after you get down to FL full time. Unless of course you see signs of you current anodes not functioning correctly.
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Old 11-07-2014, 11:48 AM   #3
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We go back and forth between CT and FL and always use zinc only. Howard
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Old 11-07-2014, 12:04 PM   #4
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I kept my boat in Lake Union, Seattle (fresh water) for two years traveling out to the salt water of Puget Sound, via the locks, once or twice a month. Always used nothing but shaft and rudder zinc and never had a problem.
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Old 11-07-2014, 02:00 PM   #5
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We move from salt to brackish to fresh regularly and always have had only zinc and never a problem.
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Old 11-07-2014, 02:50 PM   #6
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Actually, as I recall, aluminum can work in both salt and fresh water. Perhaps not ideal in either compaired to zinc and magnesium. But ...
That's how I understand it. We put Al on last year. Hobo's in brackish water that varies based on how much rain we get (25 miles up the St. Johns River in FL). So far so good. We tested -635 millivolts with zincs and wanted to get more negative. After the change to aluminum we re-tested at -1028 millivolts. We changed out a 6" x 12" x 1/2" plate, prop and rudder zinc all to aluminum. The change over was ~$10 more over zinc. Boatzincs.com has free shipping on orders over $100. They also have a brief technical discussion on this if you look thru their FAQs.
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Old 11-07-2014, 03:32 PM   #7
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Aluminum is recommended for brackish water and that's pretty much what I'm docked in but all the divers used zinc exclusively. Probably because they are most often working in marinas closer to the ocean.

I don't think travelling from salt to fresh and back again presents a problem with either metal. I've done it and never gave it a second thought.
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Old 11-07-2014, 06:56 PM   #8
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Your zinc anodes will develop a calcareous coating within a few days of being in fresh water and will stop working even when returned to salt water as the calcification acts as an insulator.

When returning to salt water just cleaning off the calcification often does not work unless you remove the anode and clean its underside to ensure good contact.

Zinc does not work in fresh water at all as its voltage potential is too low to transmit in the less conductive water. One should use magnesium in fresh water as it has a higher voltage potential and can make the jump in fresh water.
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Old 11-08-2014, 07:01 AM   #9
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>One should use magnesium in fresh water as it has a higher voltage potential and can make the jump in fresh water.<

Many folks will just not bother in FW with no bad effect.

Nervous folks can use a cable with a magnesium piece (old VW engine casting)clipped to the bonding system.

The huge danger in FW is the 120 or 240V AC system electrocuting swimmers.

If you need a summer hurricane hole , many of my neighbors have docks for rent.
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Old 11-08-2014, 08:36 AM   #10
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Four decades all over the Great Lakes, never once changed a zinc. Most of my boats never even had any including the wood boats. Now that I'm in salt I'm replacing the bloody things every 4 months. The manufacturers of outboards who have no control over what waters their motors are used in have surely given this a lot of thought and I think, are mostly, if not all zinc.

If you need a summer hurricane hole , many of my neighbors have docks for rent.
FF, Not to hijack Chesters thread but I might be interested, anything for a 50ft, are you on the Atlantic or Gulf side?
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Old 11-08-2014, 08:44 AM   #11
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Four decades all over the Great Lakes, never once changed a zinc.
Because your zinc anodes weren't working in freshwater.


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Old 11-08-2014, 10:58 AM   #12
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Four decades all over the Great Lakes, never once changed a zinc. Most of my boats never even had any including the wood boats. Now that I'm in salt I'm replacing the bloody things every 4 months. The manufacturers of outboards who have no control over what waters their motors are used in have surely given this a lot of thought and I think, are mostly, if not all zinc.
Hmm. . . Good point. My family owned a summer home on Rimrock Lake and we kept a 19' Glasply with a Merc I/O moored at a marina in the lake for many years. We never once put zinc or any other anode on the drive unit. I forgot about that. You wouldn't dare do that in saltwater.
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Old 11-08-2014, 01:21 PM   #13
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fstbttms, I see what the folks "selling" anodes recommend, I'm just saying from real world experience that not one of my old boats from the wood days to present ever had anodes "of any kind". The exception were my boats with outboards, these had some kind of anodes but I have never replaced any of them either.

Note: I'm not saying that fresh water boats shouldn't have anodes, or what, if any benefit they might be to a fresh water boat, only that none of my, or my friends boats had anodes and none were damaged in any way. In fact many Great Lakes boaters wouldn't have a clue what we were talking about.

For those not familiar with the Great Lakes, they are not brackish in any way, we are literally boating in our drinking water unfortunately. Even rusting at depth is not a big issue with anything here. I used to do a lot of diving on the lakes and over the years have brought up several outboards, some which have been down for years and (quite seriously) had every one of them running within an hour of bringing them up. Not to mention countless fishing poles, tackle boxes, anchors, tools, watches, props, etc all in pretty much the same condition that they were lost. Great fun!
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Old 11-08-2014, 01:33 PM   #14
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If your anodes are not deteriorating or you don't have any, chances are your boat's underwater metal is. The purpose of sacrificial anodes or "zincs" (whatever they are made of) is to do just that, sacrifice themselves to protect props and other underwater metal.
It's not that your prop will dissolve in a week or a month without the anodes but it's being eaten away slowly by an electric current.
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Old 11-08-2014, 02:00 PM   #15
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It's not that your prop will dissolve in a week or a month...
The boat this prop is attached to was hauled for a survey in August and everything was fine then. I took this pic two days ago.

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Old 11-08-2014, 02:25 PM   #16
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Capn Kangeroo, I too am a Great Lakes boater (most of the time).

Shaft drive boats have rarely had an issue with galvanic corrosion in the Great Lakes but over the years I have seen more and more (the why is another topic). In recent conversations with Transport Canada inspectors, local ABYC Certidied Marine Electricians and Nick Bailey (DIY Boat Magazine / Bristol Marine) we all agreed that we are seeing more and more galvanic corrosion every year. I have condemned the props on six boats this year due to dezincification.

It has escalated to the point that I am hosting the ABYC 4 day Corrosion Analysis course at Port Credit Yacht Club in March. The course will be presented by Kevin Ritz (the discoverer of "electric shock drowning").

Electric shock drowning and stray current corrosion are closely related issues and you can't study one without the other.

I/O and saildrive corrosion in the Great Lakes is now and has always been a significant problem and every claim I have investigated has been at least in part been due to lack of proper anodes.
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Old 11-08-2014, 02:32 PM   #17
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For those not familiar with the Great Lakes, they are not brackish in any way, we are literally boating in our drinking water unfortunately. Even rusting at depth is not a big issue with anything here. I used to do a lot of diving on the lakes and over the years have brought up several outboards, some which have been down for years and (quite seriously) had every one of them running within an hour of bringing them up. Not to mention countless fishing poles, tackle boxes, anchors, tools, watches, props, etc all in pretty much the same condition that they were lost. Great fun!
There are anodes on my Great Lakes boat. I asked the marina if they were manganese. They said yes but from the looks on their faces, I think they were guessing. The boat was hauled for heated winter storage and I looked at them to see if I would need to replace them in the spring and could not tell if any sacrificing had taken place. I was unable to detect anything. My limited experience kind of jells with yours.
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Old 11-08-2014, 02:45 PM   #18
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There are anodes on my Great Lakes boat. I asked the marina if they were manganese.
Perhaps you mean magnesium ?
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Old 11-08-2014, 04:01 PM   #19
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Perhaps you mean magnesium ?

Sure did. A senior moment no doubt.
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Old 11-08-2014, 10:15 PM   #20
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We keep our Tolly in SF Delta fresh water. Every 3 to 4 months I dive and scrub zinc anodes' surfaces very clean with BBQ bronze brush/scraper. Slowly but surely the zinc is disappearing… just like an anode is supposed to do! All metal parts are remaining A-OK. I feel if surfaces are kept clean on zinc it does fine as anode in fresh water. If zinc is not often scrubbed clean I feel magnesium should be used in fresh water.
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