During January 1941, production of the improved Fulmar Mk II commenced; the first Mk II aircraft was delivered to an operational squadron in March 1941. This model of the aircraft was furnished with the more powerful Merlin XXX engine; the airframe had provision for a 60-gallon (273 litre) centre-line drop tank and provision to carry a 250 lb (114 kg) or 500 lb (227 kg) bomb in lieu of the drop tank. During October 1941, tests performed at RAF Boscombe Down revealed that the 60-gallon drop tank extended the aircraft's range to . During June 1942, flight testing of the Fulmar II was conducted at MOD Boscombe Down; these tests found that the Fulmar could safely drop a 500 lb bomb during 60-degree dives at up to 310 knots. Fulmars were launched from catapults on merchant ships, a convoy defensive plan that was being evaluated at the time.