Round-neck nuts instillation

I think these T nuts are just drawn in by tightening the prop bolts.

You could tap them in gently with a hammer, or draw them in before you put the prop on either a short bolt and a large nut as a spacer...

If you were getting technical, cool the nuts to shrink them (ice/ dry ice) then they should push in easier....

But simple is better just the prop bolt thing ?

Are you refiring to the  T (X sectional) shaped collars/spacers without any thread?

If so, these are not nuts.

As Glen suggested they are tight/interference fitting spacers, that can be seated/removed by the methods he has mentioned.

A heavy duty C-clamp also works.

Tapping or freezing works. Apply a tad of lube will help them slide in place better and not shave any metal. No big hammers. Tapping with a SMALL plastic mallet type thing.

The manual states never to hit the prop shaft with a hammer (regardless of size or composition).  Correct procedure is to lightly coat the bores of the prop hub with anti-seize as well as the lugs themselves.  Using an M8x1.25 bolt (for the metric lugs 842634) and a deep 3/8 drive socket, draw the lugs into the hub by tightening the bolt.  This will get the lugs in 99% of the way.  Once the prop is installed and torqued to its specification, the lugs will seat themselves 100%.