225 hpdi lower unit prop tightening question?

I tightened my lower unit prop a few months ago, the prop had a lot of play back and forth, this past weekend I noticed that I have the same play in my prop again? if the nut is pinned how is the prop loosening up again? or is the shaft working its way out somehow?
Thank you

the shaft will have a little forward an backward play.

Yes, but it shouldn`t be over 1/8th of an inch. I would pull the prop and inspect everything, looking for rubbing or wear on the thrust washer.

I think I have it figured out, just ordered a new hub kit to replace the old one, which should fix the problem.

Thanks for the help

the thrust washer got worn out.

there are updated 2 piece thrust washers for the yamaha props