I claim the ornamental design for a propeller through-hole insert, as shown and described.
FIG. 1 is a perspective view of a propeller through-hole insert showing my new design;
FIG. 2 is a top view of the propeller through-hole insert of FIG. 1, the top view is the same as a bottom view of the propeller through-hole insert of FIG. 1, the bottom view is omitted for brevity;
FIG. 3 is a left side view of the propeller through-hole insert of FIG. 1, the left side view is the same as a right side view of the propeller through-hole insert of FIG. 1, the right side view is omitted for brevity;
FIG. 4 is a front side view of the propeller through-hole insert of FIG. 1, the front side view is the same as a back side view of the propeller through-hole insert of FIG. 1, the back side view is omitted for brevity; and,
FIG. 5 is a partially assembled view of the propeller through-hole insert of FIG. 1 into a propeller through-hole.
The broken lines are for the purpose of showing environmental structure, and form no part of the claimed design.