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As stated in the companion thread on the Grumman G-132 design, "The 1955 CNO OR AS-040502 required an ASW flying boat with the ability to alight in the open sea, up to sea state 5, in order to operate a sophisticated dunking sonar, AN/ASQ6." This resulted in the "Open Ocean Seaplane" request for proposals, dated May 21, 1956 (U.S. Navy Type Specification TS-143).
Besides the Grumman G-132 and the Convair Model 24, there was also a proposal from Convair, the Model 24, and one from Martin, the Model 313 Submaster (unofficially refered to as the P7M). This was an open ocean sonar seaplane developed from the earlier Model 290 (P5M-3) proposal, an armed boundary layer control (BLC) reconnaissance version of the Marlin. The Submaster was a four-engined high-wing flying boat type, and also had a BLC system, but this was powered by two J85 turbines, buried in outboard nacelles on the wings (some sources claim there was only one, located above the hull).
The "XP7M-1" was built only in mockup form in 1956, at Martin's own expense, but despite the company's efforts, BuAer announced Convair's XP6Y-1 as the winning entry on February 1, 1957 (at least until the whole "Open Ocean" thing was abandoned and Lockheed's land-based P3V-1 Orion was procured to fill a similar role). As aptly stated in E. R. Johnson's American flying boats and amphibious aircraft: an illustrated history, "Although Martin still had the P5M-2 in production and the P6M-1 in pre-production at the time, the P7M would be the last in a long line of Martin flying boat designs."
Attachments also taken from American flying boats and amphibious aircraft: an illustrated history
Besides the Grumman G-132 and the Convair Model 24, there was also a proposal from Convair, the Model 24, and one from Martin, the Model 313 Submaster (unofficially refered to as the P7M). This was an open ocean sonar seaplane developed from the earlier Model 290 (P5M-3) proposal, an armed boundary layer control (BLC) reconnaissance version of the Marlin. The Submaster was a four-engined high-wing flying boat type, and also had a BLC system, but this was powered by two J85 turbines, buried in outboard nacelles on the wings (some sources claim there was only one, located above the hull).
The "XP7M-1" was built only in mockup form in 1956, at Martin's own expense, but despite the company's efforts, BuAer announced Convair's XP6Y-1 as the winning entry on February 1, 1957 (at least until the whole "Open Ocean" thing was abandoned and Lockheed's land-based P3V-1 Orion was procured to fill a similar role). As aptly stated in E. R. Johnson's American flying boats and amphibious aircraft: an illustrated history, "Although Martin still had the P5M-2 in production and the P6M-1 in pre-production at the time, the P7M would be the last in a long line of Martin flying boat designs."
Attachments also taken from American flying boats and amphibious aircraft: an illustrated history
