The Sunbeam Manitou was a further development of the V-12 Maori Mk.III; work on it began by Louis Coatalen in 1917, using aluminium alloy rather than cast iron blocks, cast in blocks of three cylinders, a typical Sunbeam feature. Bore was increased to 110 mm (4.33 in), but stroke remained at 135 mm (5.31 in). The cylinder bank were at a 60° vee, with twin overhead camshafts on each bank operating four valves per cylinder. Two Claudel-Hobson carburettors and two BTH magnetos delivered mixture to the cylinders and ignited it. Fitted with a reduction gear for aircraft the engine developed 300 hp (224 kW)at 2,000rpm., later increased to 325 hp (242 kW). Unsuccessful as an aero-engine, it is best known for having powered the Sunbeam 350HP racing car.
Despite large orders for 840 Manitous, only 13 were built before production stopped. Those that were built found favour as motor-boat power-plants and only one flew trials in a Short 184 seaplane. Four were fitted to the 'Maple Leaf V' and a specially built Manitou was fitted to the 350hp Sunbeam racing car.