Red RTV. Make sure the hole is clean, I used Acetone. Heat the seal in boiling water, and it will pull over the prop flange. Then take it off, heat it in boiling water again, and put it on right this time. :lol:
After its on the shaft (the correct way), I used a cotton swab to put a very thin film of oil on the shaft, put the spring in the seal, put a very small amount of Red RTV up inside the hole, and a very small amount on the outside of the seal. Slide it in the hole, wipe off the excess, and that was five years ago.
Oh Yah, I have a VERY old O-320. It doesn't have the retainer bolt holes and it doesn't have a seating grove inside to help hold the seal.
Waiter