Help! - Sea cock problem

[chas]

My boat went into the water about 10 days ago. Before this, all sea cocks were checked, cleaned and greased. Last weekend all operated perfectly. Today, when I tried to open the heads intake (gate valve), the operating wheel turned but the valve did not open. The wheel and shaft turn freely in both directions and can move in and out by about 1/8 inch but do not appear to be connected to anything. The valve appears to be jammed shut . There are no leaks.

Can anyone suggest what has happened? Can I repair it without drying out (there are no drying berths for fin keelers in the Exe)? There is a grille on the skin fitting so I cannot put a bung in from the outside. Any help would be greatly appreciated.

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[jleaworthy]

The valve shaft is held in place by a bush which is screwed into the top part of the valve body. This bush can become unscrewed and the valve will then remain open or closed whatever you do with the wheel. I suspect that this has happened to your valve. The only remedy is to take off the upper part of the valve body and screw the bush back into place with Loctite. Perhaps a piece of polythene fastened over your valve inlet on the outside of the hull would reduce to a trickle any water entering the boat while you have the valve dismantled.

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[AndyL]

Gate valve vs Sea cock

A gate valve should never be used for sea-cock duties. If it's tight closed the thread can strip on the gate while trying to open it; if the gate remains closed you will be safe, but if it should open you would never be able to close it properly. It sounds like the thread has stripped on your valve.

For a proper fix, you should replace it with a Blake's sea-cock or a marine grade ball valve: Bronze like Groco or plastic like Marelon. Unfortunately you will have to be out of the water to do this.

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[LORDNELSON]

I really do not feel it is worthwhile repairing a gate valve; it should be replaced with a proper ball valve or a blakes valve. I would suggest a ball valve because they are much cheaper. Possible to do the work between tides by using an outside diaphragm to seal the hole during the time the tide is up but safer to haul out.

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[Guest]

If all else fails ...

A plastic bin liner with lanyards on each corner used as a 'collison mat' ...... that is placed around the hull with inlet about mid-centre of the plastic.

The only trouble with this is the bag requires pressure to 'seal the hole' .... provided by the sea pushing the plastic into the hole.

Maybe then you can dismantle and having prepared all bits and bobs to REPLACE the valve .....

But my suggestion would be to take a gentle cruise to a another place where there is a harbour wall etc. to dry out against ..... and then FIRST tape up the outer inlet BEFORE dismantling the valve ..... having again fully prepared everything for replacing the valve.

I don't fully agree that gate valves should NEVER be used as sea-cocks .... having used them myself !! BUT I do not agree with repairing or 'extending' their service life past a few years by replacement of parts etc. Its all or nothing - replace totally with new or rip out and fit better valves.


<hr width=100% size=1>Nigel ...
Bilge Keelers get up further ! I only came - cos they said there was FREE Guinness !

 

[oldsaltoz]

G,day Chas,

A friend had a leaking thru hull fitting, stowed most of the gear inside the boat to one side and hung sand bags off the boom, this gave her enough heel to get the fitting above the waterline, They then had a disk of ply and some Silastic handy ready to stick over the hole in the event of further problems: seemed pretty safe and simple, not sure how this would have gone with a bit of wave action though.

Bottom line, he fixed it, like you he had a fixed keel and no place stand her, nor even a beach big enough close by to lay her down on.

Needless to say I would not be recommending this method, but sometimes your choices are limited.

Avagoodweekend. Old Salt Oz /forums/images/icons/cool.gif..........

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[Dipper]

The wheel is attached to a shaft with a coarse thread which screws through the gate of the valve. Your thread has stripped. I advise you change the whole valve.

I am in the process of changing three of mine. One stripped like yours and the other two have some play in them so they are on their way out. I wouldn't try to do it unless ashore as it can take time especially if access is difficult. Invariably you will loosen the skin fitting as well and this will need to be removed (can be difficult) and rebedded. This is a happy hunting ground for Sod's Law.

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[brianhumber]

Re: Gate valve vs Sea cock

If you maintain and operate gates valves correctly they are just as good as the taper cocks or ball types. My gates are 16 years old, are stripped/maintained every winter, operated every time the yacht is used and never give any trouble.
As an ex engineering officer I could quote numerous failures with all three types, in anycase with the drafts that yacht valves operate in, it is not a problem to change them in water anyway if this operation is properly planned and prepared.

Brian

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[anabel]

If one of your gate valves has failed then it is quite probable that the other one is near the end of its days. I would suggest you relace both. Gate valves are not the best for underwater fittings. Use ball valves (for marine use) or the tapered Blakes valves (very expensive!). If you are going to do this job while still afloat I would suggest you carefully plan everything. Make sure you have all the tools & fittings you might require and somebody knowledgeable to assist you. Hope you don't lose too much sailing time. Good luck.

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[Trevethan]

I have a couuple of gate valves fitted in Gayle Louise. Terrible things they are and will be replaced when we lift out. One is connected to the rtaw water inlet and works well enough, though it might bweep a little...unsure if this is weeping or condensation.l

The other is on the galleydrain and has seized in the open position not amount of wd 40 has helped and my efforts to apply a little force (hand strength only) have cause a nice little leak - that meant lots of fun on a raft in cold water and I really don't want to think about what was in it......

So new ones ordwered and will be fitted forthwith.

On a similar note, a boat sunk in Exeter over the wekend and almost took another it was rafted to with it. Never knew the canal was that deep... anyway speculation is that boat owner left seacock open or one failed after lifting in and didn't wait around long enough to check all was well.....

regardcs,

Nick

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[chas]

Thanks for all the help

I am currently trying to decide whether to run her up on Bull Bank (nice soft sand) or to try to pull a tarpaulin over the hole and rely on water pressure while changing the seacock. Disadvantage with former is that all passers by will think I ran aground (many do on that bank)! Disses of latter is that if anything goes wrong more likely to sink. Perhps I had better go for Bull bank.

Anyway, many thanks for the advice and sympathy.

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[Apetts]

A can of Coka Cola down the pipe might help free the valve, but you still have the problem of turning it. I regularly used Coke on a metal to metal rudder bearing which had a habit of seizing. A can of coke down the rudder tube worked miracles after a couple of hours. God knows what it does to peoples insides!!

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