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  1. #1
    Cadet
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    Default Zinc, alumium, or magnesium anodes?

    I a'm confused on what type of anode to purchase. My houseboat is kept in fresh water and has twin Volvo Penta AQ200/280. I have another anode from other houseboat of mine and it seems very heavy for its size (zinc?) compared with a larger aluminum one that I have. I imagine that magnesium also is very light. Does it realy mater if A zinc or aluminum anode is used. After all the unit is kept in fresh water? Thanks.

  2. #2
    Admiral Dunaruna's Avatar
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    Default Re: Zinc, alumium, or magnesium anodes?

    General rule of thumb is magnesium for fresh, zinc for salt. Sacrificial anodes are made up of a cocktail of alloy, the best people to advise you as to the exact type you need is the outdrive manufacturer.

    There should be a direct correlation between the size of the anode and the material that needs protection.

    For example, my boat has a pair of 45ft alloy toons. I have a 10 pound magnesium anode attached to each pontoon.
    Watch this space......................

  3. #3
    Cadet
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    Default Re: Zinc, alumium, or magnesium anodes?

    Thank you for the reply.
    I found the mfgr.of one of the anodes and it is zinc. So I guess someone put the wrong type on. I guess I'll have to wait for a couple more weeks untill the covers come off to check to see what type of material the second dog bone type is made of so I don't mix zinc/magnesium or what ever. Thanks again.

  4. #4
    Chief Petty Officer
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    Default Re: Zinc, alumium, or magnesium anodes?

    Went to a houseboat show a couple weeks back and talked to some vendors about anodes. Seems aluminum is the best thing to get for a boat in fresh water. I was kinda curious how an aluminum anode would do any good on a house boat that is made of aluminum and he said the anodes are much softer than the hull of the boat so electrolysis sets up in the anodes before the hull, etc.
    1990 Stardust
    -Dual Chevy 305's with Volvo DP's

  5. #5
    Master Chief Petty Officer
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    Question Re: Zinc, alumium, or magnesium anodes?



    O.K., I'm not mechanical, so I will ask. What is an anode, and what does it do ??

    ~~ This boat runs on gas, NOT thanks ~~

  6. #6
    Petty Officer 2nd Class wkb2460's Avatar
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    Default Re: Zinc, alumium, or magnesium anodes?

    I've always been told Magnesium is best for fresh water.
    Aluminum was for brackish and zinc for salt.

  7. #7
    Admiral Dunaruna's Avatar
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    Default Re: Zinc, alumium, or magnesium anodes?

    204,

    An anode is a alloy that will sacrifice itself in place of the surrounding alloys (such as outdrive legs, props, toons etc etc).

    A sacrificial anode must be towards the bottom (or at the bottom ) of the 'Nobility Table'.

    I am currently blocked from posting pictures but someone (hopefully!) will post a copy of the 'Nobility Table' to clarify what I am talking about.
    Watch this space......................

  8. #8
    Seaman Apprentice SuperDaddy's Avatar
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    Default Re: Zinc, alumium, or magnesium anodes?


  9. #9
    Admiral Dunaruna's Avatar
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    Default Re: Zinc, alumium, or magnesium anodes?

    Thanks daddy.
    Watch this space......................

  10. #10
    Cadet
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    Default Re: Zinc, alumium, or magnesium anodes?

    Thank you Super Daddy! Great site for a super explanation of both salt and fresh water applications plus other components affected also.

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