Zincs wearing too fast. Why?

Discussion in 'General Discussion' started by tony1b2000, Apr 30, 2009.

  1. tony1b2000

    tony1b2000 Member SILVER Sponsor

    82
    Oct 10, 2007
    Salem MA
    350 Sundancer 2010
    496 Mag Seacore Mercruiser , Bravo III
    Hi,

    I have a 2003 280 Sundancer with Alpha gen 2 drives. It comes standard with a galvanic isolator (excuse my spelling). My boat has been in the water for 3 week now in MA and I had to pull it out for a minor repair. The new Aluminum anodes are already showing wear.

    I have heard that the bravo units come with a mercathode system which I have no idea about.

    Any suggestions how to test for problems and how to slow down this corrosive problem?

    Thanks,
    T
     
  2. Turtlesboat

    Turtlesboat Minister of Media TECHNICAL Contributor GOLD Sponsor

    Feb 4, 2007
    New York City
    1996 450DA, TNT, Caribe dink w/15hp OB.
    3126 427HP TD transmissions
    Last season I was in a hot marina (stray current in the water) and my zincs were going like hotcakes. I hooked up my zinc fish and that slowed it down a lot on the running gear but my fish is half the size now.
     
  3. 67vetteal

    67vetteal New Member

    133
    Aug 2, 2008
    Long island
    1997 250 Sundancer
    454 Mercruiser
    Google, "Galvanic Corrosion". Lots to learn. Al W.
     
  4. tony1b2000

    tony1b2000 Member SILVER Sponsor

    82
    Oct 10, 2007
    Salem MA
    350 Sundancer 2010
    496 Mag Seacore Mercruiser , Bravo III
    What did you connect the fish (anode) cable to?
     
  5. JV II

    JV II Active Member SILVER Sponsor

    Nov 17, 2007
    Newport, RI
    2016 50 Fly
    Volvo Penta D11
    Any corrosion on your drives? If not, no worries, the zincs are doing their job. Just replace them mid season. Mine were terribly pitted after 2 weeks, but made it through 6 months without any corrosion on the drives. I think I'll replace the more accessible ones this midseason.
     
  6. Hampton

    Hampton Air Defense Dept TECHNICAL Contributor

    Nov 26, 2006
    Panama City, Fl
    2008 44 Sedan Bridge
    Cummins QSC-500's
    Straight Drives
    One of two things (as I understand it, just trying to help, but not the expert):

    1) Problem with your boat's system
    2) Stray voltage in the water

    You can ask your marina if they have had any tests done, or ask around to see if anyone else has had tests or any issues. Look for cord ends in the water with power on (non GFCI (ie 30+amp)) may not trip but may cause some issues. Also, check for spiders (inside joke).
     
  7. JV II

    JV II Active Member SILVER Sponsor

    Nov 17, 2007
    Newport, RI
    2016 50 Fly
    Volvo Penta D11
    We have power cords and cable TV cables in the water all over the marina. Lots of old boats too. I seem to be the only one pulling the power cords out of the water. Many dockmates think a stray current is when the locks open at the Charles River. The marina says no stray currents. The dealer says the galvanic isolator is working and there are likely stray currents at the marina. You are not going to have any luck cleaning up the stray currents. They are probably at your marina too. Keep the cords out of the water near your boat and watch your zincs for replacement. Its the best you can do. If your '03 made it this long without corrosion on the drives everything should be working fine.
     
  8. estebanj

    estebanj New Member

    590
    Apr 2, 2007
    South Florida
    260 Sundancer
    350 Merc
    Define "showing wear." After 3 weeks, they should show "not like new," but I would say less than 20% wear.

    The mercathode system is an add-on for Bravo drives. It comes in two versions, an older "puck" system that you install on the hull next to each drive, and a newer style which installs on the drive itself.

    I would say continue to monitor your anodes and take note of install date and the rate of wear.

    Esteban
     
  9. mwph

    mwph Active Member

    Jul 8, 2008
    Lake Guntersville, Tennessee River, Alabama
    1998 250 DA
    7.4L, B3
  10. Presentation

    Presentation Well-Known Member TECHNICAL Contributor

    Oct 3, 2006
    Wisconsin - Winnebago Pool chain of lakes
    280 Sundancer, Westerbeke MPV generator
    twin 5.0's w/BIII drives

    Option #3) Accidently put fresh water magnesium anodes on a boat that is in salt or brackish water. Magnesium anodes in salt or brackish water would sacrifice at a very high rate. I’m not saying that this is what’s going on, just something else to consider.
     
  11. Aarrhh & Aarrhh

    Aarrhh & Aarrhh New Member

    426
    Nov 1, 2006
    Panama City FL
    1998 370 Sundancer,
    2004 110 Whaler
    Cat 3116 300hp
  12. Lazy Daze

    Lazy Daze Well-Known Member TECHNICAL Contributor GOLD Sponsor

    Apr 21, 2009
    PA
    Various
    Various
    Tony,

    You may very well already have the Mercathode. It replaces the anode that is bolted to the underside of the transom plate. There is also a secondary Mercathode system that can be installed - it looks like two hockey pucks that are installed on the boats' transom. It can be installed in conjuction with the transom-plate system, or by itself.

    As far as wearing away - good! Could they be wearing faster than normal? Maybe. Could be a boat near you is not protected as well as it should be and your anodes are pulling double duty.

    Keep track of how long they last - when you replace them, you could try anodes that actually are "zinc". But the whole point is the anodes wear away instead of your drive.

    Replace them when they are between 1/3 and 1/2 eaten away. don't try to stretch it out! Anodes are cheap, outdrives are not!

    Interesting info, specific to galvanic corrosion:

    http://petersmarine.blogspot.com/2009/04/galvanic-corrosion-what-is-it-and-how.html

    Hope this helps,
    Dennis
     
  13. unlvrebel

    unlvrebel New Member

    341
    Mar 24, 2008
    Clearwater, FL
    2005 220 Sundeck
    2002 Dodge Durango 5.9L
    5.0 Merc
    I'm with mwph... Tony mentions "Aluminum anodes" without mention of water type. Do you have the correct anodes for the water you are in?
     
  14. Lazy Daze

    Lazy Daze Well-Known Member TECHNICAL Contributor GOLD Sponsor

    Apr 21, 2009
    PA
    Various
    Various
    Aluminum can be used in salt or fresh.
     
  15. Presentation

    Presentation Well-Known Member TECHNICAL Contributor

    Oct 3, 2006
    Wisconsin - Winnebago Pool chain of lakes
    280 Sundancer, Westerbeke MPV generator
    twin 5.0's w/BIII drives
    Aluminum anodes can work in fresh water, barely. They work in fresh water if the drive is well sealed.

    The aluminum anodes are actually an alloy that is a mixture of aluminum and other things that when combined becomes slightly more sacrificial then the aluminum alloy used on the drive.

    Aluminum anodes in fresh water will last much longer the magnesium anodes but the drive may not last as long.

    I prefer to replace my anodes then replacing my drive, but that’s just me.
     
    Last edited: May 1, 2009
  16. Lazy Daze

    Lazy Daze Well-Known Member TECHNICAL Contributor GOLD Sponsor

    Apr 21, 2009
    PA
    Various
    Various
    That's correct - and I should have been more specific. Not all Aluminum anodes are the same. Check my link above. The Navalloy Aluminum anodes are actually less noble than Zinc. Plus, IIRC, they're made outside of Philly.

    We've been using these for a few years now with excellent results.

    However, the absolute best thing is to talk to local people/marinas to find out what works best in your area. Real life experience beats theory and science every time.
     
  17. Skuza

    Skuza Active Member

    Nov 1, 2006
    Lake St Clair, MI
    400 Sundancer
    7.4L Horizons
    Does anyone have pics of what a used up zinc looks like? Ours looks like it is mostly still there just really crusty looking. It is still original zinc since '98. We boat in freshwater and have noticed pitting on the underwater exhausts, struts and rudders ONLY. The props and tabs are fine. There are a couple older boats about 3 wells away???
     
  18. Lazy Daze

    Lazy Daze Well-Known Member TECHNICAL Contributor GOLD Sponsor

    Apr 21, 2009
    PA
    Various
    Various
    I'll look around for one, but are your anodes actually zinc? According the article I referenced above, zinc can form a crust over it when used in fresh; thereby preventing it from doing it's job. Or, your anode is not making good contact with the metal it's supposed to be protecting.
     

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