I purchased a 2 1/2" aluminum spinner i have attached a picture. It has 4 pieces the prop nut, the adapter to prop nut,the spinner and the bolt that attaches the spinner to the prop nut adapter. My question is do i attach the adapter to the prop nut to the prop nut before i tighten the prop nut or after i have tried both ways and the adapter will not stay attached to the prop nut.

You should have a backing plate in there also.

I have the backing plate im just trying to figure out what locks the adapter piece to the prop nut is it the prop nut itself or the bolt that goes thru the spinner?

you MAY need to use a different thrust washer, that second nut (the adapter) has two uses, it's a lock nut (prevents the main prop nut from coming off) and is there to secure the spinner (using the 'though bolt')
try attaching the spinner all by itself with no prop or other washers... I'm thinking you may simply have too thick a propeller and too thick a thrust washer.

normally, you'd first tighten the nut, then add and tighten the adapter nut, then add the spinner and finally the through bolt.

hope that helps!

I forgot to add, if the through bolt ends up being too long, you just cut it off as needed, and smooth the beginning of the threads to let it fasten to the adapter nut.

Many times the bolt that goes through the spinner cone is too long for the adapter. I believe that is because some engines have threads in the end of the crank. On those engines you use the stock prop nuts and then thread the spinner bolt into the crank and the extra length is needed.

David