04/30/2012. Remarks by Johan Visschedijk: "Although falling within the US Tri-Service system, this designation applies only to a foreign-built and -operated version of the Neptune. After assembling forty-eight Lockheed-built P2V-7s, the last of which was delivered to the JMSDF on June 28, 1965, Kawasaki undertook to modify its 21st P2V-7 (JMSDF serial 4637) as the prototype for a more advanced version for which design study had begun in Japan during October 1960.

The two R-3350 piston engines were replaced by Japanese-built 2,850 ehp General Electric T64-IHI-10 propeller-turbines driving three-blade propellers, while 3,086 lb (1,400 kg) thrust Ishikawajima 13-IHI-7C turbojets were substituted for the US-made J34 slung from the wing.

Designated P2V-7 Kai (= modified), this experimental aircraft was first flown on July 21, 1966. Following satisfactory results, Kawasaki produced a version with lightened airframe, longer fuselage, APS-80 search radar, twin-wheel main landing gear, and more powerful Japanese-built engines, 3,060 ehp T64-IHI-10E propeller-turbines and 3,417 lb (1,550 kg) thrust J3-IHI-7D turbojets).

Between October 1969 and March 15, 1979, 82 P-2J production aircraft (JMSDF serials 4702 to 4783) were delivered. Four P-2Js were modified beginning in 1978 for ECM (electronic counter-measures) training, air-to-surface and surface-to-surface missile simulations, target towing, and drone launching, two of these UP-2Js were fitted with ELINT (electronic intelligence) gathering equipment and redesignated EP-1J."