It seems that when you remove the lock nut the diameter and pitch are stamped in the face of the hub. Mine are 17X23.

I am looking to lower my top rpm by 500 .I am hitting the rev limiters now at 6000. The engines dynoed out at 600 hp at 5500.I am running 13% over drive at the out drive. I have twin disc transmissions but have not found the ratio of these yet.Anyone care to take an educated guess at what I should be looking for. I have read that four and five blade props are smoother with less vibration. Should I be seeking these as well.