 Grumman, wanting to take advantage of the powerful new 950 hp (708 kW) Wright R-1820 supercharged radial engine, began work on the F3F-2 without a contract; the order for 81 aircraft was not placed until 25 July 1936, two days before the type's first flight.The engine's larger diameter changed the cowling's appearance, making the aircraft look even more like a barrel, though top speed increased to 255 mph (410 km/h) at 12,000 ft (3,658 m).The entire F3F-2 production series was delivered in between 1937 and 1938; when deliveries ended, all seven Navy and Marine Corps pursuit squadrons were equipped with Grumman single-seat fighters.