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Why do English builders-Princess/Sunseeker install 2 large zincs right on the hull bottom?

Discussion in 'Props, Shafts & Seals' started by Capt J, Mar 30, 2020.

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  1. bayoubud

    bayoubud Senior Member

    Feb 19, 2017
    Looks right to me. On a fiberglass hull all is connected to the bonding strap including the shaft with a slip ring and the zinc plate. Rudders if not connected have a zinc. Nothing is grounded to the engine, all electrical components have return ground wire to the DC bus or start batteries, less electrolysis. Makes sense not be running DC current thru the engine, dissimilar metals, and seawater components resulting in no pencil zincs maintain, less electrolysis.
    This is a better explanation:
  2. PacBlue

    PacBlue Senior Member

    Jan 9, 2009
    Dana Point, Ca
    That is the missing document , without it the diagram did not add up. What engine model is it for?
  3. mapism

    mapism Member

    Aug 9, 2008
    All of their pre-common rail D28XX engines.

    But in the meantime I got hold also of a much newer installation manual, specifically meant for CR engines.
    I'm not posting the relevant pages because aside from being the Italian version, ...erm... I'm not supposed to have it.
    Anyway, the only relevant difference is a totally new section related to the connections of Rexroth electronic levers and their control units in the e/r.
    The statement which I underlined in my previous post is still exactly the same, language aside.

    Not that I expected any relevant differences, mind: I already knew that the general MAN bonding logic is valid also for CR engines.
    What I was unsure of (and still am) is whether they now ask a specific placement of the external anode bonded to the engine.
    But unless it's hidden in some fine printing which I missed, also the CR engines installation manual does NOT specify that.

    On the other hand, boat builders work jointly with engine manufacturers for anything engine-related on a new model, in order to get their advance approval, also for warranty reasons.
    So, manual aside, I think it remains likely that MAN became more strict in recent years about placing that zinc in a position where it's permanently submerged.
    I will see if I can cross-check this directly with a builder, but it will take me a while.