Hey Salty. Sounds like you have a plastic hub in your Merc Prop. I also run that set up. But the plastic hub piece is usually a one peice assembly. If it came out in 4 peices it might just be done and you need a new one.
There should only be the following:
* Large brass washer that goes on the prop shaft first
* The plastic hub that goes into the prop.
* The brass piece that inserts into the front of the prop and into the plastic hub.
* The washer that has lock tabs
* Prop nut.