Boat savvy readers may have already noticed what is wrong with the above picture. Some of you have now stopped to look at the image again and realised what is wrong. For everyone else, allow me to explain as I go through this post.
It's a through-hull valve. It is made with a bronze body and a stainless steel ball valve, so that when necessary, the water drain may be opened, or closed, as required. It is a common practice to "exercise" these valves, a procedure of opening and closing a few times every once in a while to make sure they don't seize up from saltwater corrosion.
When the boat was out of the water for bottom painting, we changed the valve on the scupper drain, Ken discovered that while the handle turned, the ball valve did not. It was indeed broken, and it was a good thing that we were replacing it. It had been replaced 12 years ago when we bought the boat, but an awkward installation inside a locker prevented us from ever exercising the valve.

Now that we are back in the water and on the dock, Ken is lubricating the mechanism of the head. He closed the through-hulls for the head intake and discharge as a matter of habit. When he reopened them to test the head, something wasn't right. I donned my snorkel, in the St George's lagoon, no less, and probed underneath the hull with a screwdriver to ascertain just what was going on. Damn it, that valve has malfunctioned in the same blasted way. This wasn't quite so bad on the hard, but now we are back in the water, there ain't no way we are hauling again. That valve had been replaced in the fall of 2008 the first time we had travelled through Florida; it had cracked during a Canadian winter, and we didn't realise it until we were in the ICW.

Wiring and electrical is essentially easy. Find connectors that for the wire size you are using. There is none of this different standards stuff, unless you count going from metric to feet and inches. Plumbing in North America on the other hand, has a few different threads, and can be tapered or non-tapered. For size, are we talking inner or outer diameter? This inconsistency had us order what we were sure was the correct size tailpipe from the U.S. The local island chandleries are a little scattered when it comes to some of this stuff; they might carry the valves, but not the required fittings. It wound up that the $#&%-ing manufacturer uses the inner diameter, not the diameter of the threads.Gee, thanks for nothing. We hate plumbing actually...wonder why?
So, we had to visit both chandleries to piece together a working system for both through-hulls. This was not an easy feat, and it wasn't wholly to our complete satisfaction, but it was all necessary, so we used what we could find, Marelon valve, PVC insert and a Marelon hose barb.
After completing my net controller duty on Thursday morning and then enjoying breakfast, I grabbed a large foam plug and jumped into the water again. This time it was my intention to stay in and babysit the plug while Ken put the valve in place. I didn't want to use a wooden plug and mess up the new paint in the outer skin fitting, but I didn't entirely trust the foam plug on its own to keep our home from sinking. Fortunately, this was close enough to the waterline that it was comfortable enough with the snorkel.
So finally, after hunting, ordering, paying, brokering, waiting, hunting locally some more and then a whole lot of swearing, these important mustnotfailoryourboatwillsink valves are changed and the hoses reattached.
Even if you are doing your due diligence and exercising these valves regularly, just because the handle turns, it does not necessarily mean the ball valve is. It wouldn't hurt to check that once in a while, too.

The 2008 head discharge valve was a solid bronze, heavy duty Groco, so it wasn't a question of a poor quality piece of plumbing, just saltwater corrosion.
Our new Marelon seawater through-hull valves will be lubricated regularly, along with all of the others from now on.
"Use it or lose it!"