Mercathode question

Discussion in 'General Maintenance/Repair Questions' started by DWABoat, Nov 19, 2019.

  1. DWABoat

    DWABoat Well-Known Member

    637
    Aug 13, 2019
    S Louisiana
    2001 280 Sundancer
    1989 220CC Cuddy Cabin
    Twin 4.3 w/Alpha Ones
    5.7 Mercruiser Alpha One
    I recently purchased a nicely equipped 2001 280 DA. Has twin 4.3’s, the Koehler 5E generator, A/C, water heater, Vacuflish, Microwave, “etc, etc, etc.” (Old Timers will get that Yul reference.)

    The twin Alpha Ones have anodes, but I do not see the little Mercathode current wire box under the transom assemblies. There is an anode on both. Further, there is no visible Mercathode Controller I can see in the engine room.

    I was a little surprised because I thought most Mercruisers came with that system, especially the nicely equipped ones.

    However, I see the EIM box in the engine room has both port and starboard Mercathode systems labeled.

    Finally my question: Is this some type of Impressed current system I am not familiar with OR are the boat EIMs all set up for the system as an available option?

    I am doing a Transom Assembly change this winter and will install the system, if it not there.
     
  2. Lazy Daze

    Lazy Daze Well-Known Member TECHNICAL Contributor GOLD Sponsor

    Apr 21, 2009
    PA
    Various
    Various
    Alpha drives don't have the Mercathode system as standard equipment. The labelling in the EIM is because Bravo drives were an option (standardized labelling).

    When you buy a Mercathode system (whether it's the one that replaces that anode or the "pucks" that attach to the transom), it's an all-in-one setup - the control box you get is the brains. Nothing is already built into the boat.
     
  3. DWABoat

    DWABoat Well-Known Member

    637
    Aug 13, 2019
    S Louisiana
    2001 280 Sundancer
    1989 220CC Cuddy Cabin
    Twin 4.3 w/Alpha Ones
    5.7 Mercruiser Alpha One
    I suspected.
    I will install the system as I do the transom assembly change next month.
    Thank you.
     
  4. Captn TJ

    Captn TJ Active Member

    872
    Sep 19, 2017
    Catawba Island, Oh
    2005 280DA
    Raymarine E80
    5.0 with Bravo 3
  5. DWABoat

    DWABoat Well-Known Member

    637
    Aug 13, 2019
    S Louisiana
    2001 280 Sundancer
    1989 220CC Cuddy Cabin
    Twin 4.3 w/Alpha Ones
    5.7 Mercruiser Alpha One
    Another Mercathode question.

    My boat stays on a trailer for most of its life. I have mostly one single day/one night use in saltwater then back home for a couple of weeks. Probably once a year it will spend a week in saltwater then back home on the trailer for a few weeks.

    For this type of usage, should I install the Mercathode system or the full zinc anode system?

    Opinions?
     
  6. Lazy Daze

    Lazy Daze Well-Known Member TECHNICAL Contributor GOLD Sponsor

    Apr 21, 2009
    PA
    Various
    Various
    What do you mean by "full zinc anode system"? Your drives already have an anode package.

    FYI - DO NOT use zinc anodes. Use aluminum anodes.
     
  7. BillK2632

    BillK2632 Well-Known Member GOLD Sponsor

    Jun 25, 2009
    Lake Norman, NC
    1999 185 Bowrider,
    Mercruiser 4.3, Alpha I
    I don't think you need a Mercathode system for Alpha's - especially since the boat does not stay in the water. As far as anodes - the general rule is aluminum=saltwater, magnesium=freshwater, although local conditions might vary some. I have magnesium anodes on mine, but it is dry stored, maybe stays in the water one or two weekends a year. I have zero corrosion issues and the anodes are probably 7-8yrs old and show no indication of erosion. The big driver of corrosion on outdrives is SS propellers - especially duo props like the BIII in close proximity to the aluminum outdrive. As soon as the paint get's compromised - chip, scratch etc, galvanic corrosion sets in between the SS propellers and the exposed aluminium on the outdrive. The anodes should be less "noble" than the aluminum and should erode before the aluminum, but in cases with a BIII there is just too much SS, that's why they have so many anodes + a Mercathode to try an disrupt the little chemistry experiment you have going on with your outdrive. All this helps, but it doesn't eliminate the corrosion. I have been there - battled the whole BIII corrosion thing on my 290da - for me an outdrive boat is fine, they perform great, but mine stay in dry storage!
     
  8. DWABoat

    DWABoat Well-Known Member

    637
    Aug 13, 2019
    S Louisiana
    2001 280 Sundancer
    1989 220CC Cuddy Cabin
    Twin 4.3 w/Alpha Ones
    5.7 Mercruiser Alpha One
    First: thanks for the response.
    Okay...”full zinc system” I only mean all the factory anodes - on the trim rams, under the transom housing, on the cavitation plate. That’s all.

    Please add to or correct my research on this:

    Magnesium anodes - best for exclusively freshwater

    Zinc Anodes - best for exclusively saltwater

    Aluminum Anodes - General purpose and work okay in both types of water. Mercruiser installs aluminum anodes stock on drives.
     
  9. Lazy Daze

    Lazy Daze Well-Known Member TECHNICAL Contributor GOLD Sponsor

    Apr 21, 2009
    PA
    Various
    Various
    OK, gotcha. You're good to go the way you are. You wouldn't hurt anything by adding a Mercathode system, but I really don't think there's any benefit in your case.

    Yes, you are correct in your research. When/if you get around to buying new anodes, be sure to get good quality ones.
     
  10. DWABoat

    DWABoat Well-Known Member

    637
    Aug 13, 2019
    S Louisiana
    2001 280 Sundancer
    1989 220CC Cuddy Cabin
    Twin 4.3 w/Alpha Ones
    5.7 Mercruiser Alpha One
    Thanks. I have both motors out right now and am installing new transom assemblies in about a week. Doing some general maintenance in the bilge while I am waiting for the parts to arrive.

    Installing Mercathode wiring right now would be easy as pie. But...if it would be a waste of money and time then I don’t want to do it.

    Just looking for opinions while I have an empty playground (bilge).
     

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