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General characteristics
Crew: four (with accommodations for a second relief crew)
Capacity: JRM Mars - 133 troops, or 84 litter patients and 25 attendants or 32,000 lb (15,000 kg) payload, including up to seven Willys MB jeeps
Water/foam load: Mars waterbomber - 60,000 lb (27,000 kg)
Length: 117 ft 3 in (35.74 m)
Wingspan: 200 ft 0 in (60.96 m)
Width: 13 ft 6 in (4.11 m) Hull beam
Height: 38 ft 5 in (11.71 m) afloat, 48 ft (15 m) beached
Hull draught: 5 ft 6 in (1.68 m)
Wing area: 3,686 sq ft (342.4 m2)
Empty weight: 75,573 lb (34,279 kg)
Gross weight: 90,000 lb (40,823 kg)
Max takeoff weight: 165,000 lb (74,843 kg)
Fuel capacity: Hawaii Mars: 6,485 US gal (24,550 l; 5,400 imp gal) Philippine Mars: 13,200 US gal (50,000 l; 11,000 imp gal)
Powerplant: 4 × Wright R-3350 Duplex-Cyclone 18-cylinder radial engines, 2,500 hp (1,900 kW) each
Propellers: 4-bladed Curtiss Electric, 15 ft 2 in (4.62 m) diameter variable-pitch propellers

Performance
Maximum speed: 221 mph (356 km/h; 192 kn)
Cruise speed: 190 mph (306 km/h; 165 kn)
Range: 4,948 mi; 7,964 km (4,300 nmi)
Service ceiling: 14,600 ft (4,500 m)
Drop speed: 138 mph (120 kn; 222 km/h)
Landing approach speed: 115 mph (100 kn; 185 km/h)
Touchdown speed: 92 mph (80 kn; 148 km/h)
Fuel consumption (cruise): 420 US gal (1,600 l; 350 imp gal) per hour
Fuel consumption (operations): 780 US gal (3,000 l; 650 imp gal) per hour
Operations duration (normal): 5 1/2 hours
Area covered, single drop: 3 to 4 acres (1.2 to 1.6 ha)
Drop height: 150 to 200 ft (46 to 61 m)
Full water tank load: 7,200 US gal (27,000 l; 6,000 imp gal)

The Martin JRM Mars is a large, four-engined cargo transport seaplane originally designed and built in limited numbers for the U.S. Navy during the World War II era. It was the largest Allied flying boat to enter production, although only seven were built. The United States Navy contracted the development of the XPB2M-1 Mars in 1938 as a long range ocean patrol flying boat, which later entered production as the JRM Mars long range transport. The aircraft first flew on 23 June 1942
Four of the surviving aircraft were later converted for civilian use to firefighting water bombers. One example of the aircraft still remains in limited service based out of Sproat Lake just outside of Port Alberni, British Columbia. The original Hawaii Mars was lost in an accident on Chesapeake Bay a few weeks after it first flew, the other five Mars were completed, and the last delivered in 1947.

US Navy Service
Named the Marianas Mars, Philippine Mars, Marshall Mars, Caroline Mars, and a second Hawaii Mars, the five production Mars aircraft entered service ferrying cargo to Hawaii and the Pacific Islands on 23 January 1944. The last production airplane (the Caroline Mars) was designated JRM-2, powered by 3,000 hp (2,200 kW) Pratt & Whitney R-4360 engines, and featured a higher maximum weight and other improvements. On 4 March 1949, the Caroline Mars set a new world passenger load record by carrying 269 people from San Diego to Alameda, CA.On 5 April 1950, the Marshall Mars was lost near Hawaii when an engine fire consumed the airplane after her crew had evacuated. The remaining "Big Four" flew record amounts of Naval cargo on the San Francisco-Honolulu route efficiently until 1956, when they were beached at NAS Alameda