IanM wrote:
....

I should point out that it would only be a simple clamp on coupling with
no key for relatively low power applications: small to medium yachts and
displacement motor boats usually with one or two cylinder diesels. ALL
the larger couplings from R&D marine either are clamp on with a keyway
or are supplied pilot bored and will have a taper + keyway machined to
fit a shaft prepared similar to the propeller end (best if identical as
then the shaft can be swapped end for end when it gets worn).

Yes, I would have presumed that as well...my essentially my only
experience w/ props is watching the machining of experimental very low
turbulence noise versions for Navy sub's in the Y-12 facility in Oak
Ridge a number of years ago. At something approaching an individual's
height per blade, they were sized for quite significantly larger shafts
than these...

--

Thanks to everyone for the help on these, I changed my answer to say that
they are propeller shafts for boats.


Rob