Re: Seized seacock
If the "seacock" in question looks anything like the pic in your link, it's almost certainly a gate valve. Gate valves are problematic for several reasons, not the least of which is that it is extremely easy to think they are closed when they are actually partially open. You need to replace that valve with either a traditional seacock or, as is more common these days, a ball-valve. Either of these require a quarter-turn to open or close, and so one can tell at a glance which position the valve is in (if the handle is in line with the flow the valve is open, if it is normal to the flow the valve is closed).
You can replace the valve with the boat in the water, as long as the thru-hull is in good condition. Just spin the old valve off and spin the new one on. It will seem like a "boatload" of water is coming into the boat while you are fiddling with the valves, but in reality it will just be a few gallons. However, if the thru-hull is at all suspect, do yourself a favor and pull the boat out of the water so that you can replace the valve and thru-hull at the same time.
Never forget them. Do something to prevent it from happening again.
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