Seacocks-stupid question!

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Mings74

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Hi all,
Pretty new to this game so bear with me. Was trying to clear a heads blockage today and was playing around with the seacock. I have two, one for the heads, and one fo the engine intake. they are the old (I presume) brass type where you unscrew the "T" shape. Until today I have only ever unscrewed ten or so turns, this seemed sufficent for both the heads and the engine (good water flow etc). Anyway today I noticed that if you unscrew it further the "T" shape becomes a plunger with about four or five inches of movement up or down. This seemed to assist in clearing the blockage. Should I have done this?, what is it for?. Initially I thought I had unscrewed it to far and was going to sink the boat!. I make a point of unscrewing the seacocks once a week or so and get out most weeks because I understand they can seize. I know it's pretty basic, but we all started somewhere right?. Cheers Ming
 
Probably best to wait until the boat is out of the water before you muck about with seacocks. I have never seen one of the type you describe or a system that combined the usual on/off function with a plunger action. From your description of taking ten turns to open, it does sound like a gate valve type. If so, they are not ideal for marine use in that debris in the valve can prevent it from closing fully. They are also subject to corrosion of the shaft operated by the wheel ( the equivalent to your T-handle) and in the worst case can snap if the valve becomes stiff or siezes through lack of use.
. However, the fact that you exercise your valves should substantially reduce the risk of this happening.
 
[ QUOTE ]
I have never seen one of the type you describe or a system that combined the usual on/off function with a plunger action

[/ QUOTE ] Nor seen one in industrial use!

Gate valves usually have a handwheel although there no particular reason why they should.

Waiting to discover what these are with interest.

Hopefully not ordinary brass though.
 
Only type I can think of with a T handle look like this?
51370_m.jpg

If so you should change it.
 
Similiar in the handdle shape, which would then screw in or out, and then when out the plunger comes into play (unless I broke it today and the boat wil have sunk when I next go down the marina!).
It reminds me a bit of the stern gland greaser (the T-handle and screw action). I'll have to get a photo of it and attempt to post it. Ming
 
We have ones that sound similar - they actually have a plate the fits flush with the hull when they are closed (old racing yacht) which you can see from outside when she's out of the water

You unscrew the handle - then pull the plunger out 4-6 inches and then there is a little bit of screw thread which keeps the handle locked out (if you don't pull the plunger bit out the seacock is only partially open)

Assuming they are the same of course ....
 
Yes - the one in the picture is cockpit drain - and if I don't remember to lock it in the out position - I can find I have a paddling pool !

If you look from the outside (probably not with a mask at this time of year!) - you will see when shut there is a metal disk which is flush with the hull - simply unscrewing it opens this a little - but pulling the plunger out pulls the disk back out of the way meaning that its fully open.

Could explain your heads blockage ?
 
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