In the post-war period, Mariners continued to operate with Coast Guard units until replaced by more modern types. The USN continued to field the type into the Korean War (1950-1953) but the fleet was eventually superseded by the Martin P5M Marlin. The last Mariner flew in 1964 (Uruguay) before the line was retired from service for good.
With production spanning 1937 to 1949, a total of 1,366 Mariners were produced for the United States and its Allies - a modest sum in the scope of World War 2 but excellent nonetheless.
Martin developed or produced a slew of PBM-related aircraft following the initial PBM-1. The XPBM-2 was a conversion of a PBM-1 to be used in catapulting experiments. The PBM-3 brought about fixed pontoon floats and was powered by R2600-12 series engines of 1,700 horsepower output - 32 aircraft were built to this standard. The PBM-3R was an unarmed transport of which 31 were converted from the PBM-3 stock and a further 18 built to order. The PBM-3C was an improved maritime patroller and carried the AN/APS-5 radar fit in a radome aft of the flight deck. Some 274 of this standard were completed. The PBM-3B were ex-Royal Air Force Mariner GR.1A ("Mariner I") aircraft returned from Britain and placed back into USN service.
The PBM-3S became a dedicated submarine hunter sporting increased operational ranges at the expense of a reduced machine gun load. Ninety-four of this type were produced and 62 more were added through converted previous marks.
The PBM-3D was another patroller but outfitted with R2600-22 engines of 1,900 horsepower. Beam gun positions now featured twin-gun armament. Two-hundred fifty-nine of this mark were delivered.
The PBM-4 was a proposed variant to carry 2 x Wright R3350 series engines of 2,700 horsepower for improved performance but this mark was never furthered.
The PBM-5 saw production reach 628 units and carried 2 x Pratt & Whitney R3350 series engines of 2,100 horsepower each. This model had several subvariants in the improved PBM-5E (with better radar), the PBM-5S (an improved submarine hunter) and the PBM-5S2 (another improved submarine hunter, also with better radar). The PBM-5A was an amphibious version of the Mariner with retractable wheeled undercarriage. This saw production total 36 aircraft and a further four converted from other marks.
While the United States was the clear operator of the Mariner line by pure numbers, the aircraft also operated with the nations of Argentina (9 units, Navy), Australia (Nos.40, 41, RAAF), the Netherlands (15 units, NAS), the United Kingdom (28 delivered out of 33 ordered, used by Squadron 524) and Uruguay (3 units, Navy).
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