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Discussion Starter #1
i put a new zinc on the shaft at the beginning of the season. just checked it last week on haulout to see how it made out over the summer. it's gone. would it corrode in 1 season or did it fall off most likely? i had brought the old one when i purchased the new one so i know it was the right size.
 

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Really depends on how you sail, how much ou sail, if your boat has stray currents, if the marina has stray currents, if the boats near yours have stray currents, if you have a galvanic protector...etc.etc..

But generally they are desigend to be replaced on a year basis. I replace mine every 6 months..just in case, besides worn out zincs are rough and cause drag
 

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Telstar 28
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If the zinc is completely gone in one season, I'd say you have an electrical leak, either at the slip, a nearby boat or on your boat, or the zinc is undersized for the task at hand. You won't know this without getting out your VOM and checking things.

Another possibility is you got cheap zincs with the wrong alloy in them.

Most zincs should last at least a season.
 

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Zince gone in one season

wchevron
Having an anode go in one season may not be problem. Need more information. Anodes should be replaced when they are 50% consumed. Are you sure you have a zinc anode?
1.What kind of boat and the location ( are you salt or brackish water)?Did you check the anode during the season? How long is your season?(What do you define as the length of the season?)
2. I s the vessel new to you and is it in the same spot it was last year?
3. Are you on a dock or a mooring? If on a dock are you hooked to shorepower? If so do you have a galvancic isolator installed on the vessel.
4. What type of propeller and shaft do you have? Materials and number of blades on the prop?
5. Does your boat have a bonding system and if so what kind of shape is it in?
6. What type of keel ? material? Internal or encapsolated? If external what kind of shape is it in? is bare metal showing?

Some pictures of the running gear and keel would be good as well.

Hope that gets you started. You can PM me if you want. Are you going to wet store or up on the hard?

John
ABYC Corrosion Tech.
 

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would it corrode in 1 season or did it fall off most likely?
It's impossible for us to determine whether the zinc depleted entirely in that time or if it fell off prematurely because it wasn't installed properly. It is unlikely that you bought an inferior zinc. Most available in the U.S. are made to Mil-Spec standards and are of high quality. Further, there are many electrical variables that can affect zinc longevity; from issues aboard your own boat or a neighboring one to problems with the shorepower system.

I find that zincs should last at least 6-9 months. Dramatically more or less and it's time to look for a reason. My advice is to install two shaft zincs next season. Your Catalina 30 has plenty of room on its 1" shaft to fit them and you will not be overzincing the boat if you do. At the very least it's cheap insurance. If you find both of them are well-depleted or missing at the end of next season, call a marine electrician in to run down the problem.
 

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Just a datapoint, but I use 2 oval zincs on the propeller shaft of my C30, which is moored in a marina in salt water.

They are about 25% used up in six months....
 

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As your data indicates you are from Rhode Island I think is safe to assume your boat is in salt water and at a marina. If it is attached to shore power I think it's fairly normal to have stray currents significant enough to cause considerable erosion of your zincs. In North America the earth is used as the return on the neutral side and so we have all kinds of stray currents. Having said that, the fact that yours is completly gone I suspect it's fallen off. The mounting scew holes in most zincs tend to be the weakest point and even a little erosion will cause the scews to either become loose or work right through the retaining holes.
 

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Discussion Starter #8
wchevron
Having an anode go in one season may not be problem. Need more information. Anodes should be replaced when they are 50% consumed. Are you sure you have a zinc anode?
1.What kind of boat and the location ( are you salt or brackish water)?Did you check the anode during the season? How long is your season?(What do you define as the length of the season?)
2. I s the vessel new to you and is it in the same spot it was last year?
3. Are you on a dock or a mooring? If on a dock are you hooked to shorepower? If so do you have a galvancic isolator installed on the vessel.
4. What type of propeller and shaft do you have? Materials and number of blades on the prop?
5. Does your boat have a bonding system and if so what kind of shape is it in?
6. What type of keel ? material? Internal or encapsolated? If external what kind of shape is it in? is bare metal showing?

Some pictures of the running gear and keel would be good as well.

Hope that gets you started. You can PM me if you want. Are you going to wet store or up on the hard?

John
ABYC Corrosion Tech.
john
1. 1978 catalina 30. narraganset bay, ri. salt water. season (in water) 6 months. i didn't check the anode during the summer. mostly day sails every weekend with a few overnights.
2. i bought it last fall. was previously located in connecticut.
3. it's at a slip with shore power. not sure about the galvanic isolator
4. brass shaft & 2 blade brass prop.
5. by bonded do you mean grounded? i know the engine is grounded to the hull. there are 2 screws that go through the hull that have wires attached to them. i painted over them when i repainted the bottom last spring. i haven't traced the wiring to them but i assumed they were for grounding. they appear to be in good condition as well as the internal wiring.
6. the keel is a lead fin keel where it is attached to the hull it is fiberglassed to the hull. the bottom 3/4 is bare lead. this past spring i put 4 coats of barrier coat & 2 coats of anitfoul on it so it's pretty well covered. the only part i couldn't paint were 2 small 4"x4" sections on the bottom of the fin where it was resting on blocks while on the hard.
 

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wchevron-

The prop and shaft are BRONZE... not brass.
 

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WChevron, I too went through my zinc this year for the first time. I have a 28' sailboat in narragansett bay but I've owned it for 5 years. I dive on the boat about every 2-3 weeks to clean the bottom and on my last dive, mid september my zinc was gone. Again first time in five years. I'm on a mooring, no dock power, the same boats around me and no sigificate changes in my electrical system. I'm assuming it's something in the water. Next year I'll have two zincs mounted
 

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Discussion Starter #12
i plan to do the same. next year i'll keep an eye on them.
 

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Try Godfrey zincs, they are twice the cost of the average zinc but they are unlikely to fall off. The set screws don't loosen because they do not depend on the zinc that is being sacrificed to hold them in place. I had good luck with them on a previous boat the required zincs on the shaft.
 

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A SEASON!!! For several years we had an old Oday next to us and we'd go through a couple of zincs a month. The diver loved it. We changed slips and guess what... zincs have lasted for several months.
Does anyone have information about galvanic isolators?
 

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Help me understand this. Installing a $200-$400 galvanic isolator will cure you from galvanic corrosion and save you from installing zincs forever?
 

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Installing a $200-$400 galvanic isolator will cure you from galvanic corrosion and save you from installing zincs forever?
Umm... no.

An isolator will help protect the boat but zincs are designed to deplete and will do so even with an isolator installed. Maybe they don't deplete as rapidly as without one, but you will still need to replace zincs periodically.
 

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Can someone explain to me how a galvanic isolator works? thanks...
 

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If zincs disappear over time they are working.. it is when they stay exactly the same that you have to worry.

However, I noticed something disturbing when I bought a replacement zinc a few weeks ago. They used to be made in CANADA but now it appears they are made in CHINA. Same brand, same labeling, higher price... With all due respect to the Chinese people, we know without a doubt that all metal allows from China are subject to serious quality control problems and consistency, even with the higher quality stuff. I wonder if this is going to be a new issue for us yachts people... BTW my Zinc was also completely gone, after a year. The last one was made in Canada.
 
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