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Cabo shaft zincs

Discussion in 'Cabo Yacht' started by Capt Maritime, Aug 1, 2022.

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  1. Capt Maritime

    Capt Maritime Member

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    I'm installing new shaft brushes on my Cabo 40, however with all these electrically hot marinas and stray electricity in and around the docks, I'm not sure if that connection through the shaft is enough to protect the struts and propellers via common bonding to the transom zinc. I'm putting together my plan when I haul the boat and I'm reaching out to the Cabo crowd to see what others are doing as I plan to install shaft zincs.
  2. Capt J

    Capt J Senior Member

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    Stick with just the transom zinc, if it's bonded correctly with the shaft brush, it won't be any different or better protecton if there's a zinc on the shaft itself. Otherwise you may notice issues with prop burn from the cavitation of the zinc in front of the prop. Some Cabo's experienced prop burn and others didn't.
  3. mapism

    mapism Senior Member

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    Pretty sure the shaft brushes as such can do nothing for the struts.
    I guess they must be already bonded internally to the transom zinc, or aren't they?

    Anyway, as was already clear in your prop size thread, I disagree with Capt J that the transom zinc (or zincs - don't you have two of them, as I recall from the pic you posted?) can be as effective as dedicated zincs for protecting everything.
    But he has a point ref. shaft zincs possibly interfering with the water flow in front of the props, which is the reason why many builders use zincs bolted on the prop nut instead.
    In your boots, I'd consider the feasibility of adapting these to your props, rather than use shaft zincs.
  4. Capt J

    Capt J Senior Member

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    Struts are tied into the transom zinc, they have a wire connected to them on the inside of the boat. Cabo's NEVER have galvanic issues, so there is no need to play engineer and add zincs. Cabo's do have tunnels and a tight blade tip to tunnel clearance and can have issues with cavitation burn on some models and some propellers. Adding shaft zincs disturbes the water flow through the tunnel an exasperates this issue. Considering they haven't built a 40' in at least 10 years, if that boat hasn't had an issue yet, what makes one think there is a reason to do anything differently? Shall we screw copper sheets on top of the entire bottom too, just in case the bottom paint isn't effective enough? You know, because that's what ship builders did decades ago.
  5. Capt Maritime

    Capt Maritime Member

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    I will be installing the Electro Guard shaft brushes, see photo, sometime this week. The struts and bonded as well to the transom zinc via the strut flange fasteners. Based on the above from Capt J, I will be sticking with the transom zinc only. Last time I was in the water, I put a mask on and inspected all the running gear. I did not see any visible burn on the blade tips on either prop. My Cabo currently has the Pro-mariner brushes installed, however the port shaft brush has fallen off which prompted the purchase of the Electro Guard shaft brush/scraper as a replacement option.

    Attached Files:

  6. MBY

    MBY Senior Member

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    Don't put shaft zincs on. Stick with the brushes and the transom zinc and you'll be fine. The 40's like clean water going to those props thats why we never installed shaft zincs at the factory.
  7. Capt Maritime

    Capt Maritime Member

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    I'm installing the new shaft brushes this week plus checking the common bonding connections for any corrosion issues. Thanks everyone. I appreciate the feedback.
  8. mapism

    mapism Senior Member

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    Well, if that was the reason, you're sort of implying that for protection alone, a shaft zinc would have made sense - which was precisely my point, since all the overzincing story is 100% BS, on plastic boats.

    OTOH, I already agreed on the other drawbacks of shaft zincs - in fact, keeping the water flow to the props as clean as solid as possible is precisely the problem addressed by the zincs I suggested, which are as effective as shaft zincs without their possible drawbacks.
  9. Capt J

    Capt J Senior Member

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    There has been NO need for a Cabo to have shaft zincs. Ever. Please present one Cabo that has had a galvanic issue. You're creating a fix for a problem that has never existed.
  10. Capt Ralph

    Capt Ralph Senior Member

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    So, There were not shaft brushes originally? Or replacing old shaft brushes?
    For shafts with NO shaft zincs, a connecting shaft brush is a must. The electrical connection thru the gear is poor.
    Shaft brushes, struts, rudders, other thru hull fittings are to be all bonded together. Hopefully to a few anodes (zincs).
    The issue I have, That one plate on the asp of the boat is going to protect from all directions of under water stray currents?
  11. Capt Ralph

    Capt Ralph Senior Member

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    My last thought; Those with burned up skin fittings forward know what some of us are concerned about.
    Those with just an asp plate either have no issues, or have not experienced any issues,, yet..

    Owners can protect their boat as they wish.
    No sense to rattle this drum any more. The beat is tiresome.

    But, with that, I'm tired of this dribble.
  12. Capt J

    Capt J Senior Member

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    yes, it had shaft brushes
  13. Capt Maritime

    Capt Maritime Member

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    Yes the boat was built with shaft brushes, however the port brush has failed. I'm installing new brushes and cleaning the common bonding connection points which are all connected to the transom zinc.
  14. mapism

    mapism Senior Member

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    Non sequitur.
    Why on earth should I present anything, just to ask a very simple question - to MBY by the way, not to yourself.
  15. Capt J

    Capt J Senior Member

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    Because your question is re-wording the same question and asking it twice and expecting a different response. Insanity, if you will. IF the boat doesn't have any electrolysis issues at all with shaft brushes and a transom zinc, nor have any Cabo's (unless there was something really wrong, poorly re-wired etc.). HOW would shaft zincs be beneficial in any way, shape, or form. Only negatives........

    However, if you want to see what wiring on a yacht should look like. Look on the internet for pictures of Cabo wiring.
  16. mapism

    mapism Senior Member

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    CJ, I'm quite used by now to your "I-know-it-all-better-than-anyone-else-on-the-planet" approach, and I can live with that.
    Most internet forums are plagued by chest-thumping contributors, so it's not like one more or less is going to make any difference.
    I would just appreciate if you could avoid commenting my own sanity, particularly when I didn't ask anything to your good self.
    You know, it would be nice to hear also from someone who knows what he's talking about, for a change.
    captholli likes this.
  17. Capt J

    Capt J Senior Member

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    I don't profess to know more than the engineers that designed and built Cabo's and determined that a single shaft zinc was the way to go!!!! Being that I've been an approved vendor for Cabo since 2004, and worked for a sub-contractor of there's prior to that. I think that I know why they did what they did. The son of one of the founders told you the exact same thing I did. You've chased away everyone that knows what they're talking about by constantly questioning what they have to say! But neither of us' answers are sufficient for you.

    One other engineer was pretty smitten on thinking overzincing eventually cause prop shafts to snap on fast boats, since the over zincing pulled a metal out of the S/S alloy over time causing the shafts to become brittle

    Getting rid of a honking shaft zinc that's both disturbing waterflow to the propellers, creating drag and robbing the cutlass bearings of cooling water when the shaft zinc inevitably slides down the shaft on a 30+ knot sportfish, was/is moving forward in hydrodynamic design from what builders did in the 80's and 90's. Some builders have gone as far as to put shaft tubes on the shafts, because just the shafts spinning in the water column also creates drag, which did pick up a solid 1-1.5 knots but then determined the maintenance wasn't worth it, others are still doing it.
  18. mapism

    mapism Senior Member

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    We already understood that you can't separate the wheat from the chaff on this matter, there's no need to reiterate that.
  19. Capt J

    Capt J Senior Member

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    Transom zinc. typo.
  20. Capt Maritime

    Capt Maritime Member

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    Thanks Capt J for all your input! I really appreciate it.