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Prop Size ?

Discussion in 'Props, Shafts & Seals' started by SplashFl, Jul 9, 2022.

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  1. Capt Ralph, Jul 15, 2022
    #21
    Capt Ralph

    Capt Ralph Senior Member

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    Well, That was another waist of time.
    As some of us have figured and mentioned. It's a plastic boat.
    Another worthless web point. Written by another word salad author filling a page of text. More wasted time.

    But, I'm tired of this.
    If you say that adding some shaft zincs on the hull pictured above is over zincing, Then it must be.
    I don't have the energy to read anymore of this dribble, so I give.

    Later gentlemen,
    rc
  2. mapism, Jul 15, 2022
    #22
    mapism

    mapism Senior Member

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    For the love of God, don't.
    The rigorous analyses which you linked so far give a whole new meaning to the old saying "ignorance is bliss".
    leeky likes this.
  3. Fiammetta42, Jul 17, 2022
    #23
    Fiammetta42

    Fiammetta42 Member

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    Liguria Italy ( boat )
    https://www.youtube.com/shorts/6jN08Zg2R38

    MAN separate transom anodes .Connected by what looks like a huge copper strip running above bilge height from the motors to the transom .
    80 mm SSteel shafts , nibral props with a 60 cm hex anode .
    Discs anodes on the metal flaps .
    On the bathing platform ( not visible ) a pair of “ shaft “ anodes wrapping around a couple of brackets .
    No anodes on the steering gear ( performance oriented boat ) but I think they are internally bonded to something …..the transom anodes , not sure .But zero signs of anything.
    20 yrs old .

    The shafts are not bonded but I guess connected to the twin disc G box direct so in some way indirectly to the engines .There’s no rubber damper i between .So share the MAN transom somewhat I guess .As well as there own clearly visible .

    The marina has piles and a range of boats , some of dubious maintenance I suspect .

    I don’t think there’s a case for saying it’s over zinced ? Feels about right .
    The mass of metal connected in what seems a web of zincs .Not just the MAN s but the sterngear .
    Last edited: Jul 17, 2022
  4. mapism, Jul 17, 2022
    #24
    mapism

    mapism Senior Member

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    We can argue till the cows come home about what over zincing is - if such thing even exists, on plastic boats.

    But the hard facts are that your anodes setup is compliant with MAN requirement of bonding the transom anode(s) ONLY with the engines, using other specific anodes for the running gear.
    As opposed to that, bonding everything to transom anode(s) is the exact opposite of what is written in MAN installation manual.
    And these are the facts, whether CJ likes it or not.

    BTW, just in case the OP is puzzled by this debate (and I could understand why!), I never said that relying on the transom anode alone, as it seems to be the case in his boat, is wrong and/or should be corrected.
    What I'm saying is that it's not compliant with the installation requirements for MAN powered boats, nothing else.
    If some builders decided to take a different route, and their setup proved to work equally well, who am I to argue?

    As an aside, I would expect your rudders, which appear to be the only bit lacking their own anodes, to be bonded internally with the swim platform or the trim tabs bolts (or both), not to the transom zincs.
    But now I'm just guessing.
  5. Fiammetta42, Jul 17, 2022
    #25
    Fiammetta42

    Fiammetta42 Member

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    Yes prob to the flap anodes are on both sides of the flap so 4 of them .
    20 yr old metal work here .The prop bolts designed to accept an anode .
    Beauty of the MAN transom anode system is as on owner you can see it ( Warm Med ) every time you swim .No hidden rotting away hard to get at pencil anodes scattered around the motors seawater cooled systems .
    I mean look at the CAT charge air cooler saga re ineffectual pencil anodes , dissimilar metals , law suits etc etc .

    Read somewhere ideally you want a field of zincs scattered around the stuff it’s meant to protect in terms of neighbours not so good protection / stray currents .
    Some indeed in the winter closed season hang additional ( old used ) zincs over the side at the stern on a wire bonded to something metallic on the boat …..= to enhance this so called field effect .
    If that’s correct the field effect theory then several smaller ones on flaps , props bathing platforms etc are surly better than one ( equal mass ) massive one on the transom ?

    Back on topic the numbers on theses spares we carry faintly stamped on the hub .
    59C2AC72-F987-4385-8EF2-A49BBAD5D85D.jpeg
    44B2EBC6-6B1B-45C2-8BAF-3D484A607EE6.jpeg
  6. SplashFl, Jul 17, 2022
    #26
    SplashFl

    SplashFl Active Member

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    36.jpg
  7. Capt Ralph, Jul 17, 2022
    #27
    Capt Ralph

    Capt Ralph Senior Member

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    Glad to see that shaft bonding brush.
    There is a resistance from the shaft to the engine block.
  8. mapism, Jul 18, 2022
    #28
    mapism

    mapism Senior Member

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    Good point, CR.
    Though interestingly, it's not how MAN powered boats are supposed to be bonded - again, according to their installation manual. In fact, since the large transom anode should only be bonded to the engine, shafts (as well as the rest of the running gear) should have their own protection.
    Usually, with zincs specifically designed to be bolted behind the prop hub (as in Fiammetta pics above, as well as in my own boat - see below).
    Or often, particularly in slow(ish) boats, with bracelet zincs directly bolted around the shafts.

    [​IMG]

    But just to reiterate, I'm not suggesting that Splash has any reasons to worry.
    Bertram obviously decided to take a somewhat different route vs. the one recommended by MAN.
    Maybe that has also something to see with the fact that, as Splash said, the boat had Detroits as standard powerplant...?
    Regardless, we are talking of two different ways to skin this particular cat, and for all I know, they might well be equally effective.

    I'd just be curious to hear from anyone else who has seen a post-takeover Bertram (in '98, IIRC) if Ferretti introduced any changes, because I'm pretty sure that they always followed the MAN-recommended (so to speak) cathodic protection in their Italian built boats, many of which have always been, and still are, MAN powered.
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