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Old 08-02-2014, 01:41   #1
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Seacock/Through-Hull Replacement

My boat was launched in summer 2001, so this summer will have been in use for 13 years. So already no spring chicken!

She was well built of good materials. I have replaced or overhauled a large percentage of domestic systems, all of the standing rigging, and 100% of the electronics, but most of the basic things are original.

Like through-hulls and sea cocks. They are bronze, not brass, and seem to be in good condition. I operate them constantly since it is my firm habit to shut off all sea cocks when I ever leave the boat overnight. But should I be worried about them? I have read some harrowing stories about sea-cocks which break off in people's hands. Do people think that through-hulls need replacing on a time-interval basis? I can't think of any good way to inspect them which would reveal deterioration, and watertight integrity of the hull is surely not something to take chances with.

What say ye?
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Old 08-02-2014, 01:43   #2
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Re: Seacock/Through-Hull Replacement

P.S. -- the same question concerns hoses and clamps -- which on my boat are also all original, apparently still flexible and sound, but . . . . . uzzled:
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Old 08-02-2014, 02:23   #3
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Re: Seacock/Through-Hull Replacement

Bronze can be inspected by looking at the color, pink is bad news and by tapping. If bronze thru hulls are inspected each time the boat is pulled and the sea cocks are working properly its not uncommon for them to last a lifetime. Hoses and clamps are different and the quality can vary. Hoses should be double clamped and hoses should be checked annually. Not all hose clamps are equal, the cheap ones are stainless straps but the screw fitting is not and they corrode.
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Old 08-02-2014, 02:53   #4
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Quote:
Originally Posted by robert sailor
Bronze can be inspected by looking at the color, pink is bad news and by tapping. If bronze thru hulls are inspected each time the boat is pulled and the sea cocks are working properly its not uncommon for them to last a lifetime. Hoses and clamps are different and the quality can vary. Hoses should be double clamped and hoses should be checked annually. Not all hose clamps are equal, the cheap ones are stainless straps but the screw fitting is not and they corrode.
So is dezincification the only deterioration bronze through hulls suffer? If that's true (?) then mine should be ok. I check them carefully overtime I haul out (every 2 or 3 months), and there is no pink sign of dezincification.
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Old 08-02-2014, 03:01   #5
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Re: Seacock/Through-Hull Replacement

Moody used good bronze fittings, good color for bronze is green bad color pink I'm sure you'll have no problems.
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Old 08-02-2014, 23:13   #6
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Re: Seacock/Through-Hull Replacement

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So is dezincification the only deterioration bronze through hulls suffer? If that's true (?) then mine should be ok. I check them carefully overtime I haul out (every 2 or 3 months), and there is no pink sign of dezincification.
The only other possible deterioration which could lead to failure that I can think of would be galvanic attack, (although it's very unlikely that you would have a more noble metal in the circuit - titanium and/or carbon fibre would be possible candidates on a Grand Prix boat but not likely here, I imagine) or electrolytic corrosion, eg due to adjacent boats being linked by the earth wire in an incorrectly wired marina.

In either case there would be visible degradation in the form of pitting.
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Old 08-02-2014, 23:46   #7
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The only other possible deterioration which could lead to failure that I can think of would be galvanic attack, (although it's very unlikely that you would have a more noble metal in the circuit - titanium and/or carbon fibre would be possible candidates on a Grand Prix boat but not likely here, I imagine) or electrolytic corrosion, eg due to adjacent boats being linked by the earth wire in an incorrectly wired marina.

In either case there would be visible degradation in the form of pitting.
My through-hulls are unbonded, so this is unlikely. Titanium would be the perfect material for this and many other marine applications, and I think hardly more expensive than bronze. I can't imagine why titanium is not more widely used.
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Old 09-02-2014, 03:08   #8
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Re: Seacock/Through-Hull Replacement

Hi
Let me tell you a little story. I was anchored in French Harbor Roatan working on my plumbing. I went to take a fitting off the top of the sea cock and the whole top of the sea cock broke off. Fortunately I had closed the valve before working on it so no water in the boat. Went to the yard and changed all the sea cocks. The point is there was no "pink" color. No evidence of galvanic corrosion. The valve was 25 years old. On close inspection the wall of the valve was very thin. There was material flaking off on the inside. It was black and looked like rust on steel when it gets thick and flakes off. Now this valve was for the cockpit drain and the galley sink. I can only guess that something poured down the sink ate the valve. There are several things that are bad for bronze that are common in the galley.
Go figure
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Old 09-02-2014, 05:09   #9
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If it's any consolation our through hulls are 37 years old and only just now coming due for replacement.
They are heavy tapered bronze plug valves though.
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Old 09-02-2014, 10:26   #10
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Re: Seacock/Through-Hull Replacement

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I can't imagine why titanium is not more widely used.

Machining it is a Bitch is probably a lot of it
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Old 09-02-2014, 10:36   #11
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Re: Seacock/Through-Hull Replacement

Come on, if all or many all of the European builders are using brass to save a few bucks, well more than a few, do you really think that any of them would even consider titanium!!! When builders like this chintz out and put in the worst crap they can for skin fittings and sea cocks where else are they cutting corners where you can't see it. I'm far from naive but I sure never expected this type of mindset from someone building yachts.
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Old 09-02-2014, 10:41   #12
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Re: Seacock/Through-Hull Replacement

are they tapered bronze type? Those are usually heavily built. one option is to pull only the thru hulls on next haulout and replace them.... leave the seacocks in place and screw out the thru hull. The thinnest part of the system is the threads on the mushroom shaped thru hulls. You could pull just one out and inspect it well before deciding what to do next.
Regarding Titanium, it's cool stuff but not perfect for everything. It galls terribly, so any moving ti on ti application (like a ball valve ball or tapered seacock body) would likely be problematic.
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Old 09-02-2014, 10:59   #13
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Re: Seacock/Through-Hull Replacement

De-zincification is a problem with brass which can have up to 35% zinc. Some bronze's are bronze in name only i.e. manganese bronze which is actually a brass.

I have only surveyed a few Moody's but all had silcon bronze throughulls and seacocks. Silicon bronze has less than 5% zinc and often less than 1.5%.

Real bronze throughulls will last longer than you or your grand children will. I know of fifty year old bronze throughulls/seacocks in perfect working condition.

If the bronze is from China ... all bets are off.
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Old 09-02-2014, 11:54   #14
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Re: Seacock/Through-Hull Replacement

Find yourself a Surveyor, with an Ultra Sound.

He can measure the wastage at the interface where the mushroom passes through the hull. This will be where 90% of the wastage will be, on a good bronze skin fitting.

You won't be able to tell by looking, as the wastage wont be visible until you break it open, then you will see an granular structure between the inner and outer surfaces.

A good bronze skin fitting has a life of about 20 years when unbounded, and left to it's own dvises. That doesn't mean you should forgo ultra sounding at every survey.

Lloyd

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My boat was launched in summer 2001, so this summer will have been in use for 13 years. So already no spring chicken!

She was well built of good materials. I have replaced or overhauled a large percentage of domestic systems, all of the standing rigging, and 100% of the electronics, but most of the basic things are original.

Like through-hulls and sea cocks. They are bronze, not brass, and seem to be in good condition. I operate them constantly since it is my firm habit to shut off all sea cocks when I ever leave the boat overnight. But should I be worried about them? I have read some harrowing stories about sea-cocks which break off in people's hands. Do people think that through-hulls need replacing on a time-interval basis? I can't think of any good way to inspect them which would reveal deterioration, and watertight integrity of the hull is surely not something to take chances with.

What say ye?
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Old 10-02-2014, 06:16   #15
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Re: Seacock/Through-Hull Replacement

I think your boat, as it is made by a more upmarket EU builder will have DZR brass seacocks and through-hulls. Bronze isn't used in the EU and hasn't been for a while. Better than brass though, but I'm not happy with it. It, like plain brass is made with about 40% zinc and it can dezincify and become brittle and a danger, as it does in domestic plumbing systems occasionally. It is also dependent on good quality control in manufacture. Too easy to make a bad batch, which can sink your boat. Why have the stuff and take an avoidable risk when true bronze is cheap and available and which lasts forever. Witness the 16C canons brought up made of gunmetal bronze. Stupid situation in my view.

The test is to take the surface finish off with a tungsten scraper, then sand down a bit and to look for pink bits as a sign of dezincification. Maybe to remove a sample fitting and cut in half. I will check all of mine the next haul-out and change for bronze or titanium if there is much pink.

Operation of valves is necessary, but not enough as many bronze and dzr valves have pure brass balls, so can work, but be on the point of failure and in need of replacement. If they are of this type then should be changed out after I think 5 years.

Any gate valves should be junked. They can appear to work, closing down, but may have their full operation blocked with marine growth. I just pulled one to find that exactly that happened. They have no place below the waterline, plus I don't think pure bronze (or even pure DZR) gate valves are made, so shouldn't be in such a location for that reason alone.

As to hose clamps. Mine, like everyone's are stainless crap. Last week I pulled to test a clamp on the prop shaft seal and it broke off in my hand. The bolt snapped. There was just a small bit of corrosion on the surface. I found stress corrosion cracking. They should really all be changed for titanium and certainly replaced when any rust is seen that can't be removed with a little polish. Particularly any rust on a bolt. Another one for the list.

Hoses - I asked that question here a short while ago and I had the impression the hose would go stiff before cracking, so to look for that first. By the way, any steel reinforced hose needs watching. I have had hose fail and blow where the steel has been corroded, particularly at end fittings so any corrosion at the ends is a prompt for replacement. Bulges too.
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