Question:  Can anyone think of a reason *not* to remove the coupling, clean
it thoroughly and then squirt in enough clear RTV silicone sealant to fill
it?  It might be a little more pliable than the original black rubber
stuff, but it ought to work, unless anyone out there can tell me of
something in-the-bottom-of-a-'60 that will rot out the sealant...
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yes- it's easy to buy a NEW one.   i dont think they cost much.