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Shaft zincs & painting inside of exhaust

Discussion in 'Cabo Yacht' started by CSkipR, Mar 4, 2014.

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  1. CSkipR

    CSkipR Member

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    Typically where do you mount the shaft zinc? I've heard its best to mount a few inches from the strut although mine were 36" up the shaft from the strut.
    Also I heard it was important to tap the zinc with a hammer to get a good connection? Do you do that for the zincs on the trim tabs as well? I only have zzincs on shaft (1), trim tabs (8) and the large one on back of hull.

    What's the best way to paint inside the exhaust since I can't reach but about 3 ft inside? Should I tape a paint brush to a stick or is there a better way?

    I am cleaning running gear to put propspeed on and some additional bottom paint, zincs, and strainers.
  2. Capt J

    Capt J Senior Member

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    Your boat is not supposed to have shaft zincs. The shaft is bonded inside of the boat and that runs to the transom mounted Diver's Dream zinc plate. I cannot remember on the trim tabs.....Buy Zimar zincs, they are mil spec quality instead of the Camps that have concrete and rocks in them...the Zimar's have a bead inside that always makes contact.

    You don't need to paint that far into the exhaust. No sunlight, no water flow, and no growth.

    Prep is everything with the Propspeed and you have to paint it on super fast because it hardens up really quick.

  3. CSkipR

    CSkipR Member

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    Capt J,
    Wow the shafts have always had zincs. I trust your knowledge but would like to confirm before removing the shaft zincs. Unfortunately the zincs are neither Camps or Zimars they are from West Marine (forgot name). Not impressed with them.
    On the exhausts when I am sitting with full fuel they are nearly full of water approximately 1-2" from top. They get some barnacles almost 4 ft back in exhaust. Not a lot but they are there.
    Skip
  4. Old Phart

    Old Phart Senior Member

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    I dunno
    Some people wish they had your problem of a constant supply of barnacles.

    BBC News - Scraping by on barnacles in Spain
  5. dsharp

    dsharp Senior Member

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    The shaft zincs a very slightly undersized so you tighten them up then hit them to spread them out a little then tighten the fasteners again. Never heard about hitting them for a better connection.
  6. CSkipR

    CSkipR Member

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    From what the boat yard says you tap them so the little tit inside connects to the metal. Actually two people confirmed this on another site. Don't know just what they have said.
  7. Capt Ralph

    Capt Ralph Senior Member

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    Been a while so please forgive me for not remembering the vendors brand name. When I serviced boats, a shaft zinc had a copper pellet in the inside of the zinc. On the outside was a molded target that said "strike here". The idea and implied instructions was after clamping the shaft zinc in place, rap this spot with a hammer to further set the copper pellet onto the shaft thus improving an electrical connection from the anode to the shaft.
    30+ years later, not thought of since, it comes up here.
    Could this be an old habit from a lost era? Are these zincs still around that have this copper pellet for better connection? Anything close?

    Plain theory, the zinc has to be between the material you’re trying to protect AND the material that is a threat. The better electoral connection it has with the material it is trying to protect, the better.
    I also remember a copper cutting washer on the old R zincs, They would compress and make an electrical connect on th surface to protect.

    These last many years I have been spoiled to Isolated Green Wires, Galvanic protection, Not in a marina full of C AH's, and the results of proper diver service. And, I don't dive any boats anymore (40 years +).
    Tiss good, yes...
  8. Capt J

    Capt J Senior Member

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    I have heard this and it is true, some shaft zincs do have the copper pellet in them..... Order Zimar zincs.....They're sold in Fort Lauderdale and are great mil-spec zincs.

    Look at your shafts inside of the boat right behind the gears. There should be a flat bar that contacts the shaft mounted to the stringer, this should have a bonding wire on it that goes back to the transom mounted zinc. Your boat should have this.
  9. Old Phart

    Old Phart Senior Member

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    I dunno
    Close enough?

    Shaft Zinc Anodes
  10. Capt Ralph

    Capt Ralph Senior Member

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    Yep, You & J are on top of it. I'm sure this is where the comment of "tap on them with a hammer" is from.

    If not hit in the correct spot or on a zinc without the pellet, you may be counter productive.

    Also, the lower 3" of my 10" exhaust fills with barnacles. At the end of the day, the gasses and hot water wash them out.
  11. Bill106

    Bill106 Senior Member

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    Do NOT put shaft zincs directly in front of the strut, it will block good water flow to the cutlass bearing. I prefer to mount them a couple inches behind the shaft log where it exits the hull and it's usually out of the direct path of water flow to the prop.

    A couple of tie wraps and a stick will allow you to use a roller perpendicular to the exhaust tube to get antifouling farther up.
  12. mwwhit1

    mwwhit1 Senior Member

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    I used the Zimar zincs for the first time last year. They definitely lasted better than the camps. Wear more evenly. I think they are worth the price increase.
  13. CSkipR

    CSkipR Member

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    Capt J you are correct there is a flat bar that contacts the shaft that is grounded. That's very interesting to know. As to why my boat has always had shaft zincs who knows. When I changed them this week the old ones (little over a year) were in fair shape although they did have some signs of deterioration. Since I have already purchased and installed I wouldn't think they will hurt anything so will leave them on. Thanks for the info.
    Regarding the exhaust issue I believe with these engines CR900 V8 and 700 gallons of fuel in cockpit this boat is stern heavy. As stated when full fuel scuppers are almost underwater. Maybe 1-2" clearance. It runs a little bow high even when fully trimmed down.
    Skip
  14. Capt J

    Capt J Senior Member

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    It didn't come from Cabo with Shaft zincs.
  15. Caltexflanc

    Caltexflanc Senior Member

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    I will pile on as another very happy long time user of Zimar zincs. I ordered them from one of my favorite suppliers, Deep Blue Yacht Supply, a preferred source for all below the water line items.
  16. squarepants

    squarepants New Member

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    zincs with bronze insert

    I have always used Godfrey shaft zincs and I have always been satisfied.
    They have a brass core that provides constant contact.
    They are pricey, but well worth the investment. I boat in Wellfleet Ma where prop and underwater gear are always subject to corrosion.