FIG. 1 is a top view of the propulsion device body; FIG. 2 is a bottom view thereof; FIG. 3 is a front view thereof; FIG. 4 is a rear view thereof; FIG. 5 is a right side view thereof, the left side view being a mirror image thereof; and, FIG. 6 is a side top perspective view of the propulsion device body. The broken lines are for illustrative purposes only and form no part of the claimed design.