A6E1, A6E2 and A6E3 were fitted with an Armstrong Siddeley air-cooled V8 180 hp engine giving a maximum speed of . A6E2 was fitted with the Ricardo CI 180 hp engine but this was not satisfactory and the Armstrong-Siddeley was refitted. A6E3 was later re-engined with the Thornycroft 6V , a slow revving marine engine. It was proposed to combine two Rolls-Royce Phantom engines with the Wilson transmission system on the A6E1 but this was rejected on grounds of expense. A6E2 was eventually refitted with the AS V8 180 hp.