Built as a successor to the PBM Mariner, it had better engines, an improved hull, and a more conventional tail. The XP5M Marlin prototypes were based on the last PBM-5 Mariners, the company designation being Model 237. The type was heavily improved, again leading to the P5M-2 (Model 237B), which was redesignated SP-5B. A number of P5M-1 models were also used for training, designated TP-5A (after 1962).
A VP-40 SP-5B after the last operational U.S. Navy flight of a Marlin in 1967
A French P5M-2 in 1957
The Marlin was designed as a gull-winged aircraft to place the engines and propellers high above the spray. Power was provided by two Wright R-3350radial engines. The rear hull did not lift sharply from the water at the tail, instead rising up steadily, a Martin innovation; this gave the aircraft a longer base of flotation and reduced "porpoising" over waves.
The prototype had nose and tail turrets with twin 20 mm (0.79 in) cannon in each, as well as a dorsal turret with two 0.5 in (12.7 mm) M2 Browning machine guns. The cockpit area was the same as the Mariner's. It first flew on 30 May 1948.
The first of 167 production P5M-1 aircraft was produced in 1951, flying on 22 June 1951. Changes from the prototype included a raised flight deck for improved visibility, the replacement of the nose turret with a large radome for the AN/APS-44 search radar, the deletion of the dorsal turret, and new, streamlined wing floats. The engine nacelles were lengthened to provide room for weapons bays in the rear.
The P5M-1 was followed by 116 P5M-2 planes. These had a T-tail to put the tail surfaces out of the spray, an AN/ASQ-8 MAD boom at the rear of the tail-tip, no tail guns (the gun position replaced by the antenna for the AN/APN-122 Doppler Navigation Set), better crew accommodation, and an improved bow to reduce spray during takeoff and landing.
The final Marlin flight was carry out by VP-40, to San Diego Bay on 6 November 1967.
U.S. Coast Guard
Seven P5M-1Gs and four P5M-2Gs were built for the United States Coast Guard for air-sea rescue service, but they found the planes difficult to maintain and surplus to requirements. They were subsequently transferred to the U.S. Navy, which redesignated them as TP-5As and used them as training aircraft, since they had no provision for armament.
The French Navy took delivery of ten former U.S. Navy Marlins between 1957 and 1959 to replace Short Sunderlands in maritime patrol service, based in Dakar, Senegal in West Africa. They were returned in 1964.
Modified P5M-1 with upgraded electronic and anti-submarine equipment, eighty conversion later redesignated SP-5A.
Seven former USCG P5M-1Gs returned to Navy as crew trainers and one former P5M-1, later redesignated TP-5A.
Updated production model, 108 built for the U.S. Navy and 12 built for the French Navy, United States aircraft later redesignated P-5B. P5M-2 featured T-tail in lieu of low mounted horizontal surfaces in P5M-1.
Most P5M-2s were modified with upgraded electronic and anti-submarine equipment, later redesignated SP-5B.
Four P5M-2s built for the USCG, later transferred to U.S. Navy as P5M-2s.
P5M-3 (Model 313)
Revised as P7M-1 Model 313 SubMaster with a single turbojet engine mounted. Mockup built in 1956 but lost out to Lockheed P-3 Orion.
One SP-5B is located at the National Naval Aviation Museum at Naval Air Station Pensacola, Florida. This aircraft, BuNo 135533, is believed to be the last remaining example of the Marlin. It is now displayed inside the new hangar (as of the spring of 2010) and much of the exterior has been restored. The restoration is being financed by the museum and the Mariner/Marlin Association.
Data from United States Navy aircraft since 1911, Jane's all the World's Aircraft 1957–58, American flying boats and amphibious aircraft : an illustrated history