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Sea cocks: Bronze or composite?

Discussion in 'Technical Discussion' started by JohnHansen, Jan 27, 2020.

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  1. JohnHansen

    JohnHansen New Member

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    Hi!

    My 1998 Princess 60 is on land for some work during the winter. I have checked the sea cocks, and the bigger sea cocks seems in good order. The smaller sea cocks around 1" (there are 5 or 6 of them) are corroded - they all survived tapping with a hammer (not too hard) and they will probably work for a year or 2. But now the boat IS on land, I consider replacing them - but to what? Should I stay 'traditional' with bronze-through-hull and bronze cocks, with the troubles of finding high quality bronze components and the risk of corrosion. Or should I install composite through-hull and composite cocks? And which brand should I go for?

    What are your thoughts and experiences?
  2. Capt Ralph

    Capt Ralph Senior Member

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    If you were to read the fine print in Forespars Marelon cock manuals, it instructs you to operate theme monthly and kept lubricated with Forespar grease.
    I discovered this the hard way after installing a couple in my personal fish boat many years ago. Went to open one one day and it had seized from internal fouling. Then the handle failed.

    Quickly I learned a valuable lesson.

    I know there are other composite mfgs out there that may have a better product but I know they will never be stronger than bronze.

    Since then, I only install better bronze thru hull flanged fittings and cocks.
    Don't skimp on proper bonding also.
  3. Beau

    Beau Senior Member

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    Are there different qualities of bronze like SS?
  4. Capt Ralph

    Capt Ralph Senior Member

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    Yes.

    Bronze is a mixture of different alloys.
    Everybody has their own recipe pending supply of resources and expense to forge these resources and to cast/machine the end product.

    You probably have realized a different recipes used in China vs the New-England area of the US.

    I am sure across the Atlantic (O P from Denmark), other mfgs have different mixture/cast/machine processes also.

    Remember, it's keeping your ship afloat, not a place to skimp.
  5. Beau

    Beau Senior Member

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    yes, that was my point. But how does one determine the grade except by manufacturer?
  6. Capt Ralph

    Capt Ralph Senior Member

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    By better manufacturer.
    The novice my not know and relies on us old farts.
    Rule #1, #2 and many more; Avoid **** from China.
    My old crapper experience is Groco first, Perco & Buck Algonquin, very close second.
    IMO, nothing else to tap on.
    Don't ask me about that Apollo junk.

    I have no idea of the quality from the other side of the pond. Denmark may have another list of quality & not so ?? over there.

    Like some mfg's here
    Last edited: Jan 27, 2020
  7. mapism

    mapism Senior Member

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    Here, the manufacturers widely recognized as the best for this stuff are Maestrini and Guidi.
    Hard to name the absolute best, since both have their strength, depending on the specific product.
    It's just worth mentioning the innovative "non stick" valves recently introduced by the latter, with no steel ball.
    I heard nothing but praises about them so far, but only time will tell for sure.
    If and how easily they can be sourced in the US, I really don't know.
    Pretty expensive stuff even when sourced factory direct, anyhow.
  8. Capt Ralph

    Capt Ralph Senior Member

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    It's not a states call. O P from Denmark.
    Thanks to mapism for opening our eyes to some east bronze shops.
  9. mapism

    mapism Senior Member

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    Good point, I wasn't paying attention to that.

    @ JohnHansen:
    aside from what you can find directly in DK, I'm pretty sure that you can source the whole Maestrini range from the online chandler SVB.
    You can't go wrong with their stuff.

    Btw, I forgot to mention that when it comes to composite vs. bronze, I'm also in the bronze field.
  10. bayoubud

    bayoubud Senior Member

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    I remember reading about a US valve mfgr sourcing their valves in China. They had major problems with corrosion, our last boat had them. I think Apollo was the brand.
  11. menkes

    menkes Member

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    I think you ignore composite valves and thru hull too quickly
    check the NZ manufacturer https://www.trudesign.nz/marine/products
    I know yachts that used these cocks for more then three years and they work smoothly like new !
    by the way, it doesnt matter of sea cock material you use,
    its good practice to go over all the seacocks once a month or two and move then on/off
    i do it on my yacht with excelent results
  12. Capt Ralph

    Capt Ralph Senior Member

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    Interesting
    The U S Distributor is in here in Jax. I'll swing by one day and have a chat and maybe look over some of their TD products.

    I don't think ignore is the correct term here.
    Maybe just hardened and old fashioned. After a life time of discovering what works and does not work, some education the hard way; I just may be one of those ole dawgs that new tricks are just not going to happen.

    Not to talk bad of a product I have never handled.
    I work with what I know.

    I hope the OP does check out these TD products. They do look impressive.

    menkes
    Thx for your post and thoughts.
  13. mapism

    mapism Senior Member

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    +1.

    In fact, when I decided to replace the mains seacocks in my current boat after purchasing her (when she was already 13 years old), I did check out also composite parts.
    But back then - and I don't think the product range has been extended in the meantime - the max size available was 2".
    And while my boat is no superyacht by any stretch of imagination, I needed 3".

    That aside, also in my experience good quality bronze stuff, properly grounded, work just fine.
    So, any alternative is actually a solution to a problem that I don't have.

    Btw, menkes, lasting three years in perfect conditions ain't such an impressive result, to be honest.
    I've seen 30 years old boats where the original bronze fittings were replaced to stay on the safe side, cutting in half the old parts afterwards out of curiosity, only to find out that they could have lasted another 30 years...
    Though arguably that kind of bronze quality is harder to find, these days.
  14. Capt Ralph

    Capt Ralph Senior Member

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    AAAh
    Most of my 42 year old bronze is fine. 15 years ago we pulled and found some questionable thru hull out side fittings. Seems the backing plates were leaking, wet bronze and bonding strap at these locations sucked or loose. This hardware was to the heads way under the decks. Way out of sight.
    All replaced with new back plates and flange bolts. New straps run.
    During our autopsy, all really looked good and could of lasted longer.

    I dissect everything that comes of any boat we work on. Amazing what we find sometimes.
  15. Capt J

    Capt J Senior Member

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    I'd replace them. I prefer Guidi over Maestrimi, Maestrimi's sea strainers and their baskets (I know unrelated to the thread) are the worlds biggest POS's.

    I deal with a new Sunseeker right now that has over 1/2 of it's seacocks out of plastic and the remainder in Bronze, the plastic ones don't freeze or get stiff, but just working them, they flex a lot more than I'd like.
  16. Capt Ralph

    Capt Ralph Senior Member

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    And what brand are those flexing handles?
  17. mapism

    mapism Senior Member

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    You are making me curious, on which boat(s) did you come across them?
    They are pretty rare also among Italian builders - at least the half decent ones, which invariably use Guidi for strainers.
    Not that I'm aware of any specific flaw in those built by Maestrini, but pretty sure the Guidi ones are built like a brick sh!thouse.
    Coming to think of it, I can't remember to have ever seen a boat, no matter how old, where they had to be replaced.
  18. Capt J

    Capt J Senior Member

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    Both, new Princess and Sunseekers use the Maestrimi's with the tiny criss cross holes/slots in the strainer baskets for the air conditioning strainers that you have to brush for half an hour with a tooth brush to get clean. The lid O-RINGS are garbage also and always swell and fall out of the little groove they sit in.
  19. Capt J

    Capt J Senior Member

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    Some sort of Marelon sea cocks. The handles or body flex on all of the Marelon seacocks from what I've seen.
  20. bayoubud

    bayoubud Senior Member

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    Exactly why I prefer bronze thru hull components. No corrosion or electrolysis is tempting but plastic is not as durable as bronze. Maybe ok on other plumbing but not thru hulls.