With a total of 1,305-1,752 kW (1,750-2,350 hp) the SM.81 was well served, even if individually the engines were underpowered. The maximum speed with the AR.125 engine was , with others it was from . Cruise speed at its best was , but there were reported values of up to . The extra power of many engine-sets was valuable in high and hot conditions, but their larger diameter was sometimes enough to reduce maximum speed by adding more drag. Even so, the aircraft was faster than the Junkers Ju 52, its most direct equivalent.