I have a decent looking C21 78" prop with no logs. Does anyone here have an idea how one would market such a prop? I have no idea how to find anyone needing it or parts of it. Thanks!

I would get the full p/n off the hub, then check the McCauley website for specs & application info. See what length(s) are OK and what it fits, then list it on barnstormers, here, etc.
FWIW I bought an 88" C201 not long ago- no logbook & unknown time in service, although it had 1500 hours (TBO) n the airplane it came off of. I paid $1000 for it as a core, immediately had it OH'd ($2500+) as well as converted to oil-filled ($1500+).

The C-21 AKA “the tooth pick” has been orphaned for years, McCauley will recommend replacing it, most have been replaced with newer props, six or seven years ago I had a 78" on my Franklin, no one could rebuild it, no bearings or seals available, as in most aviation if you beat the brush hard and long enough you may find the parts, some folks are married to the C-21, I was lucky enough to get a field approval to replace mine, if it’s in good condition there may be people that still need them.

172heavy wrote: some folks are married to the C-21.

I've talked to a couple of people lately that have pointed me toward the Stinson forum as a source of those wedding bells. I'll join up and see if anybody needs it over there. Thanks for the replies!