The prototype was converted to a single-engined aircraft powered by a 200 hp (149 kW) Curtiss V-X-X engine, also in a pusher configuration, during 1917, being redesignated as the Curtiss HS-1 (for H model with single engine) [REF].
The HS-3 was a further improved version with a new, wider hull flat-sided hull, that eliminated the typical Curtiss sponsons.