A pair of bracket fastening parts (7, 12, 91, 92, 121, 122, 161, 162) are provided on a side of the main body in an adjoining relationship, each bracket fastening part including a plurality of bosses (32 to 35, 72 to 75, 102 to 106, 132 to 137) arranged in a convex polygonal pattern and a plurality of ribs (37 to 42, 60, 80 to 84, 110 to 115, 140 to 146) connecting the bosses in a prescribed pattern. At least two of the bosses of one of the bracket fastening parts are shared by an adjoining one of the bracket fastening parts. Thereby, the engine can be adapted for multiple applications while minimizing an increase in the weight of the engine.