Seacock

 
As no one has jumped in with a reply I'll give it a try.
Where is this sea-cock?  My Mk1 one doesn't have any as standard. Can you supply a picture? I guess it will be a standard fitting from one of the major manufacturers.
 
Let us know and well see what we can do.
 
Regards,
David H.

The skin fitting can be left on the boat and the sea cock should just unscrew off the skin fitting, although there might be some thread lock or sealant which might make it difficult to remove, if you are removing the seacock try and prevent the skin fitting from turning as this will break the seal between the skin fitting and hull.