Changing Zincs

[ChrisS]

I'm curioius to know how often people check their zincs on their boats. I am having my bottom professionally cleaned for the first time since I bought it lat June (I did it myself through September, but it's just too cold now). I haven't heard about electrolosis problem in my marina, but who knows?

I know there's a zinc on the shaft, but should there be one on the rudder or hull as well?

Also, when I was crewing on a J-105 a few years ago, the owner hung a large zinc over the side whenever it was in the slip. Is this precaution worth taking? If so, where do you buy the jumbo zinc, and what's the best way to set this up?

 

[Shadowfax]

I check mine whenever I'm in the water. Here on the east coast, Chesapeake Bay, the boats can be out of the water 4 to 6 months a year so replacement of zinks is on the spring checklist. If you find that your zink is not lasting a season then you, or your neighbor, or possibly the marina, has a bad ground or polarity issues somewhere.

You only use zinks on metal, so the hull and rudder on Ericsons, or at least the Ericsons I've seen, don't require zinks, because they are fiberglass. I suggest you look up electrolysis here, or on any of the marine pages and it will explain the process, but basically what you are doing is allowing the electrolysis to eat the sacrifical zink [a less "noble' metal] and not your stainless steel shaft, or bronze prop.

Your friend who drops the large zink over the side at the dock may be doing it to combat electrolysis and also I've seen them used when attached to the shrouds as a better path for lighting strikes. These zinks are available at WM etc.

 

[jkm]

For a few years I was at a Marina with many old boats. For some reason I was blowing through zincs every four months and I suspected that the condidtion of the docks and boats was the cause.

When I moved to a new Marina with "Classier boats" the problem went away and the beer was imported!!!!!!!

Now to answer your question about hanging a zinc over the side. One guy on my old finger did just that and swore by it. He bought his at a commercial boiler manufacturer in LA. For about $50.00 he got one that was 24 inches long.

I Googled "Commercial Boilers" and the name Ace Boiler company came up and that's where he ordered it from.

That's my .02s worth.

John

 

[Frank Langer]

As others are indicating, I think zinc wear depends on many factors, including whether there are other boats nearby emitting electrical currents, which will cause your zinc to corrode more quickly. It is also affected by the chemical composition of the water (eg. how much salt) and by how fast the water circulates around the boat (ie. current vs. stagnant) and perhaps other factors as well.
If you zinc needs replacing more than twice per year, you could hang a larger zinc over the side, but you could also install a galvanic isolator, which tends to isolate your boat from marina/dock electrical currents.
I have a couple of zincs on my prop shaft, which I replace twice per year--boat is in the water year-round.
Hope that helps a bit.
Frank.

 

[Richard Elliott]

Zincs

I inspect/replace twice/year in Puget Sound using a diver who also cleans the bottom. I have two shaft "footballs" and a zinc on my three-blade Max-Prop.

 

[Frank Langer]

Richard,
Do you also replace the zinc on your propeller every 6 months? I also have a zince on my Varifold folding prop, but it is quite expensive to replace, so I have been replacing the two zincs on my prop shaft every 6 months as well, but have been told that this would also be enough to protect the prop and not to "waste my money" on also replacing the more expensive prop zinc. Once the water is warmer, I'll take a more careful look at the condition of the prop zinc to see if there are signs of it eroding.
Frank.

 

[Richard Elliott]

Zincs

The prop zinc lasts much longer, at least a year. It's expensive, but I'm not willing to risk damage to an expensive Max-Prop.

 

[Sean Engle]

My boat was in a hot marina as well - so I had two on the shaft and one big 'fish' over the side, clamped to a cleat that was grounded to the engine block...

Make sure you check the pencil zinc in your exchanger as well...

//sse