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Catalina/Capri 25/250 Sailor's Forums

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Sacrificial Annode

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frich
Captain

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USA
418 Posts

Initially Posted - 04/01/2002 : 21:37:33

I am in the process of stripping my swing keel and have noticed annodes on either side of the keel. I have heard of differing views with regards to replacing these, some say yes. Others swear by attaching a sacraficial annode to a conducting cable, then attaching this to a shroud and throwing this overboard while docked.

Any opinons on this matter?

Frank Rich
84 C25

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Douglas
Master Marine Consultant

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1595 Posts

Response Posted - 04/01/2002 : 22:03:53

If you are in a slip and there is shore power available you might want to have zinks. If you are trailering there is no need. If there is no potential I.E. a source of electrical differance possative to negative then there is noting to worry about. If however you are in a slip with other boats and shore power there is a good chance one of the boats will or has an electrical leak. Electrical current flowing from the boats metal parts protruding into the water. This differance in electrical potential will attack the softest metal it can find as close as it can find it. In a worse case senario you could find what is called a hot slip. This is where the shore power wireing from the dock or dock power box is shorting into the water. In this case any adjacent boats will be subject to deteriorization of any metal underwater parts. Putting a saceaficial zink on your keel in most cases will take care of a normal situation. In a hot slip they would only last a short time. If you trailer there realy is no need for a zink other than a small one on your outboard.

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frich
Captain

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USA
418 Posts

Response Posted - 04/02/2002 : 07:03:44

Doug;
is there any way of testing the water in my slip w/ regards to it being "hot"

If you are in a slip and there is shore power available you might want to have zinks. If you are trailering there is no need. If there is no potential I.E. a source of electrical differance possative to negative then there is noting to worry about. If however you are in a slip with other boats and shore power there is a good chance one of the boats will or has an electrical leak. Electrical current flowing from the boats metal parts protruding into the water. This differance in electrical potential will attack the softest metal it can find as close as it can find it. In a worse case senario you could find what is called a hot slip. This is where the shore power wireing from the dock or dock power box is shorting into the water. In this case any adjacent boats will be subject to deteriorization of any metal underwater parts. Putting a saceaficial zink on your keel in most cases will take care of a normal situation. In a hot slip they would only last a short time. If you trailer there realy is no need for a zink other than a small one on your outboard.

[/quote]

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Douglas
Master Marine Consultant

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1595 Posts

Response Posted - 04/02/2002 : 11:58:45

I don't know how you could test your slip. I might consider however talking to the people in adjacent slips. Have a good look around at how well the marina or slips are maintained. Have a look at any power boats and their out drives for zinks and their condition. I guess you might say it would be tribal knowledge. But WOW thats a good question. Ill work on it some more.

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pbarr
1st Mate

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USA
54 Posts

Response Posted - 04/10/2002 : 19:02:56

I just bought a 1978 Catalina 25 swing keel. I do not see any zincs on the keel. Where/how should they be installed? If you have a picture that would be great.

Phil

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frich
Captain

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USA
418 Posts

Response Posted - 04/11/2002 : 07:15:27

Phil
On my 84 swing keel, i have a circular annode on either side. It looks as if it is screwed directly into the keel with some type of bushing.
I may be wrong here as there is a buildup of oxidation on them.

I just bought a 1978 Catalina 25 swing keel. I do not see any zincs on the keel. Where/how should they be installed? If you have a picture that would be great.

Phil

[/quote]

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Ken Cave
Navigator

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USA
148 Posts

Response Posted - 04/12/2002 : 01:00:12

I had my 25 Catalina at two marinas for four years, and not had a zinc installed on the keel. In fact I took the one off that was on it when I purchased it! Just think. What can go wrong with the keel? There are no electronics you have to worry about that are connected to the keel. The cable is stainless steel. Your engine, whether it is an outboard or inboard have zincs built in. There is nothing there to screw up-even if your marina is hot!! If you do pull up your keel with zincs in place, you better be sure there is clearance on the trunk to do this-of you will cause extensive damage to the trunk.

I am at a "hot" marina with my Cape Dory 28, and only have one zinc on the boat which is wrapped around the propeller shaft-and replace this zinc every eight months.

Ken Cave

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The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.