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Old 05-05-2013, 06:10   #1
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Marelon seacock failure

I have a Marelon seacock in the forward head and the handle broke off in my hand when I tried to open it this weekend. It's stuck in the closed position at least. I am not impressed with Marelon. Anyway, can I replace seacock without hauling boat? I don't see how, but though I could at least ask the question. If not, can I salvage the current one to make it functional until I haul the boat? Thanks.
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Old 05-05-2013, 06:17   #2
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Re: Marelon seacock failure

You can change it in the water . . .

Insert wooden plug or nerf ball into thru hull from outside. That will mostly plug the hole . . . you will probably still get a bit of slow leaking, but the boat will not sink. It should not take very long to swap out the seacock if you have all the parts and tools ready.

I have never seen a good 'jury rig' for a broken handle but perhaps someone else has. If you broke the handle, then the ball is probably well frozen in any case. It helps to move them every once in a while to keep them freed up.

Out of curiosity, what size valve is it? Heads usually use 1 1/2" discharge (smaller for intake) and at least in my experience, while smaller ones do break, those 1 1/2" don't break very often. If its the smaller intake line, when you replace it, you might think about putting in a 1 1/2" one and then bush it down to the hose size.
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Old 05-05-2013, 06:19   #3
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Re: Marelon seacock failure

I think the larger Marelon seacocks are pretty strong, but the handles do feel weak. Personally, what I have done in the past is used them for the 1.5" discharge line, but not for the much smaller intake line. In any case, is it broken open or closed? If closed, I'm not sure how you could safely get the thing open. If open, I would put a plug in from the outside if you just want to seal it off, then you could put a temporary inline valve in the hose in order to be able to shut the water down. Double clamp all the hose connections, and keep an eye on them until your next haulout!
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Old 05-05-2013, 06:22   #4
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Re: Marelon seacock failure

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Originally Posted by CHM View Post
I have a Marelon seacock in the forward head and the handle broke off in my hand when I tried to open it this weekend. It's stuck in the closed position at least. I am not impressed with Marelon. Anyway, can I replace seacock without hauling boat? I don't see how, but though I could at least ask the question. If not, can I salvage the current one to make it functional until I haul the boat? Thanks.
Which type of Marelon seacock is it? Does it have a flange or is it just an in-line valve threaded to a thru-hull fitting...?
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Old 05-05-2013, 06:26   #5
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Re: Marelon seacock failure

I had seen a mechanic change a seasick by putting a wooden plug on the outside under water then replaced the valve.
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Old 05-05-2013, 07:23   #6
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Re: Marelon seacock failure

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Originally Posted by CHM View Post
I have a Marelon seacock in the forward head and the handle broke off in my hand when I tried to open it this weekend. It's stuck in the closed position at least. I am not impressed with Marelon. Anyway, can I replace seacock without hauling boat? I don't see how, but though I could at least ask the question. If not, can I salvage the current one to make it functional until I haul the boat? Thanks.
The handle broke off right? Is there still something left on the seacock that could be turned with a wrench? A square extension of the shaft that the handle fits over? If you found a new handle could you install it on the existing seacock? If so, contact the manufacturer for a replacement handle.
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Old 05-05-2013, 08:23   #7
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Re: Marelon seacock failure

There is a plastic plug covering the screw holding the handle onto the valve. That plug is designed to fit tightly into the thruhull and prevent water leakage while you work on the seacock. So just dive over with that plug and stick it in the thruhull. There is a little "handle" on it that you can tie a string to so that when you are done you can just pull it out without going back in the water.

At least that is how all of our Marelon seacocks are designed.

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Old 05-05-2013, 09:28   #8
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Re: Marelon seacock failure

Sticking seems to be an issue for all ball valve type seacocks both plastic and metal. The metal ones are usually strong enough to just put an extension on the handle and force it to move. Marlon seacocks seem more likely to break a handle or the stem connecting the handle to the ball.

It's easy to avoid the sticking, just open and close the valve a couple times a year.

Does anybody have a theory why ball valves stick? The balls all ride on something like teflon. Once you break them lose, they work fine for several more months. Could it be the stem that sticks?
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Old 05-05-2013, 09:43   #9
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Sticking seems to be an issue for all ball valve type seacocks both plastic and metal. The metal ones are usually strong enough to just put an extension on the handle and force it to move. Marlon seacocks seem more likely to break a handle or the stem connecting the handle to the ball.

It's easy to avoid the sticking, just open and close the valve a couple times a year.

Does anybody have a theory why ball valves stick? The balls all ride on something like teflon. Once you break them lose, they work fine for several more months. Could it be the stem that sticks?
It's marine growth.
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Old 05-05-2013, 09:58   #10
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Re: Marelon seacock failure

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Does anybody have a theory why ball valves stick? The balls all ride on something like teflon. Once you break them lose, they work fine for several more months. Could it be the stem that sticks?
Oh, Oh, jumping up and down with hand raised in the air. I know this..

The brass ball valves will fail at the stem due to micro galvanic corrosion where the zinc in the brass is sacrificed to the more noble copper. The remaining copper stem is porous and weak and will snap off. Well the stem is weak to begin with and suffers from some torgueing anyway.

Bronze valves suffer from this less as the zinc content in bronze is much less then in brass. The dezincing of brass also effects the strength of the valve and thru hull and they sometimes will break too, if the brass valves have a high zinc content.

BTW Brass and bronze come in different alloys and not all are the same. So some brass valves are better then others. Really Bronze valves should be used for seacocks, but of course they cost a lot more.

Marlelon is made with nylon as the primary material. Nylon will over time absorb water and will swell just a little. Its a small rate, but it happens. The swelling will make the ball harder to turn, and will torque the stemto the point where it will snap.

The stem in all ball valves is the weak point in the design. Given that most seacocks and ball valves in general are not operated that much, they have a tendency to snap off over time. This as the ball is generally much larger then the stem and will have some buildup of "stuff" at the ball /teflon border that makes the ball hard to turn anyway. Seacocks also get hard growth growing around there too.

That is why you should always operate seacock handles at least once a month.
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Old 05-05-2013, 10:48   #11
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Maine Sail,

it's the straight connection to thru-hull, no flange. I will likely replace it with a flanged seacock and backing board. This is left from a prior owner.

Others: thanks for the replies. The actual square key sheared away from the inner ball so the handle and screw fell out with the broken square key. It is for a 3/4" hose draining the head sink. not a big deal. The seacock is in the closed position. I exercised it regularly, etc. It still broke. I thought about a foam plug and changing it, but have noe experience doing it that way.
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Old 05-05-2013, 11:04   #12
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Maine Sail,

it's the straight connection to thru-hull, no flange. I will likely replace it with a flanged seacock and backing board. This is left from a prior owner.

Others: thanks for the replies. The actual square key sheared away from the inner ball so the handle and screw fell out with the broken square key. It is for a 3/4" hose draining the head sink. not a big deal. The seacock is in the closed position. I exercised it regularly, etc. It still broke. I thought about a foam plug and changing it, but have noe experience doing it that way.
If you can live without it until next haul-out, I would then remove the valve and thru-hull fitting and put in a Groco fitting with the flanged adapter. The problem with that is that you will like it enough to change all the other fittings too
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Old 05-05-2013, 11:11   #13
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Thank you, Jedi. I only have one Marelon thru hull on the boat - the broken one. I may change the entire thru-hull to bronze Groco, but not decided yet.
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Old 05-05-2013, 11:53   #14
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Re: Marelon seacock failure

Yes you down front jumping up and down waving your hands! Stop that, you'll get a black eye.

Hi Sailor Chick, When I was but a ladd it was common to see gate valves with brass stems screwed to thruhulls. The stems failed exactly as you describe. The zinc went out of them and they turned into soft copper sponge.This was in the sixties and seventies. In the eighties people started using ball valves and more flanged seacocks. I have rarely seen failed stems on metal ball valves.

I recently did some research on seacocks to see what their stems were made of as the subject came up in another thread. I checked with Groco, Perko, Buck Algonquin and Apollo. I consider them all to make quality products. All but Apollo use brass stems. Non of them seem to de-zinc. I don't know why. Maybe they are not exposed to enough water?

In fact the only two stems I've seen broken from any of these manufacturers were a couple of bronze Apollo stems. Both were from 2-1/2" Seacocks and broke when the owners used extra force to free a stuck valve. They just looked undersized for the job. That was a long time ago and I bet they've fixed the problem by now.
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Old 05-05-2013, 12:24   #15
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Re: Marelon seacock failure

Actually I had a 3/4" apollo stem break on a past boat and even saw this happen many a time on land in older ball valves. Apollo valves as a rule are Ok, but I think sometimes the metallurgy gets off a bit during manufacturing.

If the seacocks are bonded and the hull zinc's kept in good order and the bond wires don't corrode then the micro dezincing does not happen.
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