My cockpit drain fittings are more like sink drains... a thin SS lip that doesn't sit very proud of the surface, rather than a standard throughhull.. maybe look for something like that.
Well, you're dead on, Faster. I have those drains now. In fact, they ARE sink drains (2" bar sink drains). But all the attachments are pot metal, zinc, chromed brass, etc. All corroded originally and crumbling. I was planning to replace the corroded parts and put the sink drains back in. I found a few problems though:
1) It's logistically very difficult to get everything attached due to the bends in the hose (even with flexible hose). Long story, just trust me.
2) The hardware that screws on (all of which I had to replace because the original stuff had disintegrated) was very difficult to find. Although all plumbing/hardware stores carry these parts, the threads all vary. I had to buy 8 sets before I found 2 that matched what I have.
3) While installing one of these back in, one of those screw on nuts broke. Why? Because I put a wrench on it. That's pretty bad, and I'm not sure I want those parts to be the things that are supposed to keep our boat from sinking (our cockpit drains lead to hoses that connect to seacocks below the water line).
So after all that, I started to rethink the original drains and though about just switching to a real cockpit drain that was designed for this type of installation and isn't pot metal. Of course, there are problems there too.