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Old 08-05-2018, 14:54   #16
rbk
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Re: Replace this seackock & thru hull, right?

Two things, as MonkeyButler points out it is in fact brass, just look at it. Secondly the NPT fitting threaded directly to the NPS fitting of the thru hull is another big no-no. Keep the thru hull, get a proper flanged adapter or flanged seacock with NPS threads and the female outlet will now be NPT to fit your elbows, barbed fitting ect.

On a side note they do in fact make plated bronze but the plating never outlasts the bronze.
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Old 08-05-2018, 14:56   #17
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Re: Replace this seackock & thru hull, right?

You have a Ball Valve not a seacock ! REPLACE IT ! if it were me use a seacock bronze if you have the cash if not a marlon one will have to do . Seacocks are mounted on Pads glassed and are screwed right to the hull !
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Old 08-05-2018, 15:16   #18
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Re: Replace this seackock & thru hull, right?

Is your boat a beneteau??
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Old 08-05-2018, 15:19   #19
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Re: Replace this seackock & thru hull, right?

It's hard to tell, but I don't see a bonding wire attached to that thru-hull. After you get the metallurgy / composition of your inlets sorted out, you may want to ensure you have appropriate bonding on all your thru-hulls and other on-board systems.
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Old 08-05-2018, 15:31   #20
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Re: Replace this seackock & thru hull, right?

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Originally Posted by NevisDog View Post
From that excellent article posted by Scout 30 above (post #9) it seems there may be some argument for keeping the thru-hull (mushroom) and replacing everything else. That would be so easy to do (not even requiring a haul-out, if you use one of those little plastic umbrella things to stop the flow temporarily, or just get wet and pop the bung in from the outside). I can certainly see some merit in keeping that single-hole thru-hull instead of replacing with a bronze flange fitting plus requisite large grp internal doubler and three extra bolt holes. (Geeze if that hull is cored then the extra bolt holes, if they miss the portion of solid hull around the fitting, could spell disaster!) Provided the mushroom is located in a well-protected location, as mentioned in the comment to Scout's article, there isn't necessarily much wrong with the existing bronze thru-hull.

If he did decide to keep the bronze thru-hull but replace the brass valve (and of course toss that silly elbow), how do we ensure pipe threads are compatible? I'm faced with similar dilemma so any advice welcome, especially if it makes things less costly.
A proper flanged seacock will have threads that match the thru hull's threads. A seacock can have a ball valve or a tapered cone but it will also have a round or triangle shaped flange at the bottom. A ball valve bought at Home Depot, even if it's bronze, will have different threads & should never be used. I'm a fan of Spartan's tapered cone seacocks but any of these will work fine:

https://www.spartanmarine.com/all-pr...ks-for-adapter
https://www.defender.com/product.jsp...262&id=3741432
https://www.defender.com/product.jsp...264&id=3683709
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Old 08-05-2018, 15:39   #21
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Re: Replace this seackock & thru hull, right?

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It's hard to tell, but I don't see a bonding wire attached to that thru-hull. After you get the metallurgy / composition of your inlets sorted out, you may want to ensure you have appropriate bonding on all your thru-hulls and other on-board systems.
This observation of lack of bond wire is most important comment yet! If indeed there was no bond wire, I would pull the boat out of the water soon, then yank on the valve with your gloved hand. If the assembly does not break off in your hand, the threaded thru hull fitting may still be sound. Of course with 19 years underwater, it should be removed and re-bedded at the least.

Clean it all up with CLR, then grab a wrench and pull the 90 bend and valve off the thru hull. Make sure you install a ground wire and decent marine thru hull valve.
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Old 08-05-2018, 15:48   #22
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Re: Replace this seackock & thru hull, right?

My 1986 pearson and current 2005 beneteau have no ground wires to thru hulls with never a problem..... different theories.
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Old 08-05-2018, 16:59   #23
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Re: Replace this seackock & thru hull, right?

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A proper flanged seacock will have threads that match the thru hull's threads. ...
So what do you think of those glass-reinforced-nylon seacocks, combined with their ABYC approved 'load bearing collars,' from TruDesign.nz? Should have the same straight thread, right? Shouldn't get damaged when you drop that toolbox on it, or accidentally step on it when the hatch is open? ("More resistant to knocks than solid bronze.") Plus no extra holes to drill in the hull, and no more corrosion! - a win-win???
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Old 08-05-2018, 18:28   #24
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Re: Replace this seackock & thru hull, right?

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So what do you think of those glass-reinforced-nylon seacocks, combined with their ABYC approved 'load bearing collars,' from TruDesign.nz? Should have the same straight thread, right? Shouldn't get damaged when you drop that toolbox on it, or accidentally step on it when the hatch is open? ("More resistant to knocks than solid bronze.") Plus no extra holes to drill in the hull, and no more corrosion! - a win-win???
I don't have any experience with them but they look to be very well thought out and a simpler install. There have been some good reviews of them by members on this site that have installed them.

https://www.defender.com/product.jsp...264&id=3683709
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Old 08-05-2018, 18:36   #25
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Re: Replace this seackock & thru hull, right?

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My 1986 pearson and current 2005 beneteau have no ground wires to thru hulls with never a problem..... different theories.

It may be a theory, but ABYC standards and industry experts seem to feel it's pretty important. Your mileage may vary.

http://stevedmarineconsulting.com/wp...tems138_05.pdf
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Old 08-05-2018, 18:47   #26
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Re: Replace this seackock & thru hull, right?

I would highly recommend Spartan Marine tapered cone bronze seacocks https://www.spartanmarine.com
My seacocks are 34 years old and still perform flawlessly. They are also bonded to a sintered bronze grounding plate.
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Old 09-05-2018, 04:58   #27
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Re: Replace this seackock & thru hull, right?

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I would highly recommend Spartan Marine tapered cone bronze seacocks https://www.spartanmarine.com
My seacocks are 34 years old and still perform flawlessly. They are also bonded to a sintered bronze grounding plate.
I've got a 1" Spartan sitting on my desk right now which I will install at my next haul out. Kind of expensive but boy is it a beautiful hunk of bronze.
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Old 09-05-2018, 05:52   #28
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Re: Replace this seackock & thru hull, right?

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It may be a theory, but ABYC standards and industry experts seem to feel it's pretty important. Your mileage may vary.

http://stevedmarineconsulting.com/wp...tems138_05.pdf
The issue of bonding through hulls seems to be a US thing (possibly wider). Certainly UK and many European boats do not have through hulls bonded together.

On my own yacht only the S/S rudder shaft is connected to the hull anode. The S/S propshaft has its own anode. The Bronze through hulls are all separate and will remain so.
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Old 09-05-2018, 06:18   #29
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Re: Replace this seackock & thru hull, right?

If your "surveyor" missed this I would be concerned with what else he missed. Was this an insurance survey or pre purchase? It might be a good idea to go through the whole boat with some knowledgable friends or hire another surveyor.
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Old 09-05-2018, 14:56   #30
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Re: Replace this seackock & thru hull, right?

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The MS58 cast into the part is a designation for a grade of brass CuZn39Pb
Thank you for that. I had no idea any valves were marked with the alloy designation, and now I am going to be checking mine.

FWIW I looked at some data sheets for the alloy and found that it has poor resistance to corrosion compared to single phase brasses (this is two phase, and one phase is particularly rich in zinc, and hence prone to corrosion). So this is the type of brass that can turn into a very weak sponge-like structure. Needless to say, this is scary. Replace soon.

BTW the reason this alloy is popular is that it literally is the standard (100%) for machinability. Great for manufacturing, less so for us.

Live and learn...

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