Originally Posted by FF
There are 2 seperate items , the seacock and the thru hull that serves it.
The seacock is usually bolted in place with 3/8 bolts thru the hull, or today's method by gluing a mount pad inside the hull.And bolting to it.
Either way the unit is at least semi perminiant as it does not have to be removed for service , just perhaps replacement after a decade or 5.
5200 is OK as removal is seldom if ever required
The threaded thru hull screws into the sea cock from outside the boat.
It may need to be inspected at times (normal on Pax for hire boats) or when it turns pink from some electric source.
A tool stuck in and turned with a wrench will remove it quickly and a quick clean up with a wire brush will show if its fit to be reinstalled.
The thru hull reinstall uses a sealant NOT A GLUE! to make the process easy the next time.
Fred is spot on. I'd only add that Groco now gives the option of a "two-piece seacock." The base (they call it a flanged adapter) is bolted (and inevitably epoxied) to the round backing plate. The backing plate in turn is epoxied to the hull and this makes for a very robust connection. The valve, or operating part of this assembly, then threads to the flanged adapter. If you use the right sealant, as Fred notes, both the valve and through hull can be removed or replaced if necessary without disturbing the backing plate or flanged adapter.
Also, the flanged adaptor has the correct threads to accept both the through hull (NPS threads) and the valve (NPT threads). Lots of warnings out there about trying to marry through hulls into old style seacocks or valves with mismatched threads.