sentences:  The less-common Left Hand engines were typically used in buses, because the rotation matched rear-engined transverse installations.Boats equipped with two engines would typically use one Left Hand and one Right Hand, so that the torque from the propellers would cancel each other out, without the need for a complex reversing gear on one side.As a two-stroke diesel engine that does not use crankcase aspiration cannot naturally draw in combustion air, the blower is inherently necessary to charge the cylinders with air for combustion.