I have a buhk 20 in 32ft yacht. I have lost the prop. Measuring in the water which is not ideal I make the ratio out to be 1:12 on 1 inc shaft. It is a Swanson so Australian. Does that sound ok as apparently not common in aus?

1:16 is the sae taper for a 1" dia shaft
Small end of taper is .828"
Length of taper is 2.750

You could have 1:12 ,, you never know with props

1:12 is the taper for a shaft in a commercial vessels. Glenn at DH Porter Propellers is the man to talk to

If a 1:16 prop was fitted onto a 1:12,, that may be the reason you now have no prop