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  1. #1
    Join Date
    Feb 2011
    Location
    Pacific Northwest ish
    Posts
    93

    Default Zinc, Magnesium, or Alum anodes fresh water use. bf50hp

    HI for several years we are getting build up of crusty material on our anode, lower leg, and thoughout the interior cooling passages of our motor
    to the point where our tell tale water exit gets plugged up and does not piss water.

    the fiberglass hull sits in clean fresh water all summer.
    we pull it out flush vinegar through it, push weed wacker plastic wire up the tell tale and after several attempts clean out the system,
    yes we change the thermostat and impeller annually.

    but why are we getting this build up? are my anodes not working?
    while reading forums i'm reading zinc for salt water. Magnesium for fresh and aluminum fits in there somewhere.
    Our Honda dealer says Honda doesn't give them any guidance on what to use. They sell what Honda supplies.


    any suggestions?

    here's some pics. they are to big to post (and my pc doesn't reduce them) here so the following is a drop box link.

    https://www.dropbox.com/sh/17b7sb2rm...i1sS6x8ka?dl=0

    cheers
    Eric

  2. #2
    Join Date
    Sep 2008
    Location
    Hague, Virginia, USA
    Posts
    4,257

    Default Re: Zinc, Magnesium, or Alum anodes fresh water use. bf50hp

    WOW - that certainly does not look like a fresh water motor. Are you sure the anode(s) are making good contact with the base? When I mount a new anode, I typically use emery cloth and buff up all the contact points on both the anode and the base. On my 225 and on several other engines I've seen, there is an extra ground wire the connects from one of the mounting bolts for the anode to the main engine mount frame. Not sure if that would do any good on your setup.

    As for material, I'll try to upload a fairly definitive article on the subject. Bottom line is that magnesium would probably be best for your application.

    Anodes_Different types.pdf
    CHawk 25 DLX

  3. #3

    Default Re: Zinc, Magnesium, or Alum anodes fresh water use. bf50hp

    Quote Originally Posted by chawk_man View Post
    WOW - that certainly does not look like a fresh water motor. Are you sure the anode(s) are making good contact with the base? When I mount a new anode, I typically use emery cloth and buff up all the contact points on both the anode and the base. On my 225 and on several other engines I've seen, there is an extra ground wire the connects from one of the mounting bolts for the anode to the main engine mount frame. Not sure if that would do any good on your setup.

    As for material, I'll try to upload a fairly definitive article on the subject. Bottom line is that magnesium would probably be best for your application.

    Anodes_Different types.pdf
    When I install zincs I use a multimeter to ensure continuity, and periodically check with the meter.

    It may be worth pulling the crud and testing what it is made of...i.e. magnesium, calcium, etc. That can be done with a cheap aquarium kit, and tell you the material that is actually corroding.
    Last edited by TritonFisher; 09-21-2018 at 07:47 PM.

  4. #4
    Join Date
    Dec 2015
    Location
    maplevalley WA
    Posts
    5,049

    Default Re: Zinc, Magnesium, or Alum anodes fresh water use. bf50hp

    Hondas are notorious for plugging up for some reason. Flush it in a barrel of water regularly ideally after each use and store it in the running position so it fully drains. Saltaway works great for flushing the silt and minerals that are in fresh water it also dissolves the corrosion. You can get saltaway at any walmart well worth the investment. Just dump it in the barrel and let it idle a half hour or so a couple times a year.

  5. #5
    Join Date
    Apr 2018
    Location
    Australia
    Posts
    348

    Default Re: Zinc, Magnesium, or Alum anodes fresh water use. bf50hp

    I would be getting a marine electronics man in to check for stray current on your mooring before further damage occurs, this has nothing to do with the anodes.

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