Chris,


All props that I know, or ever saw, have a hole drilled in their center.
It is around this hole that the props are balanced during their production.

This engine, as well as all other model engines that have a 3/4/6 bolt mounting pattern also have this 10 mm center stud, sometimes without a thread, to center the prop on its 10 mm center hole.

Use it for what it was meant.