FIG. 1 is a front right perspective view showing a first embodiment of a snowmobile side panel according to our design;

FIG. 2 is rear elevation view thereof;

FIG. 3 is a front elevation view thereof;

FIG. 4 is a right side elevation view thereof;

FIG. 5 is a left side elevation view thereof;

FIG. 6 is a top plan view thereof;

FIG. 7 is a bottom plan view thereof;

FIG. 8 is a front left perspective view showing a second embodiment of a snowmobile side panel according to the design, being a mirror image of the first embodiment;

FIG. 9 is a rear elevation view thereof;

FIG. 10 is a front elevation view thereof;

FIG. 11 is a left side elevation view thereof;

FIG. 12 is a right side elevation view thereof;

FIG. 13 is a top plan view thereof; and,

FIG. 14 is a bottom plan view thereof.

Throughout the Figures, the broken lines immediately adjacent the shaded areas represent boundaries of the claimed design while all other broken lines illustrate unclaimed portions of the snowmobile side panel and form no part of the claimed design.