Early in 1943 the US Navy felt the need for a fighter as a backup for the Grumman F6F Hellcat which would enter service in the middle of the year. The natural step was to look at the fighters then available in the USAAF, the P-51 and P-47.
Because of its preference for radial engined aircraft the US Navy decided to order 25 navalized P-47 Thunderbolts.
Adaptations included a strengthened undercarriage and an arrester hook aft of the tailwheel. The first batch of 10 aircraft was delivered to the US Navy in December 1943 with the designation FR-1 Seabolt. This is not to be confused with the Ryan FR-1 Fireball from 1946. The manufacturers letter R was reassigned to Ryan in 1945.
The Navy carried out carrier tests with the Seabolt in February 1944. The pilots were not very enthusiastic about the aircraft, finding it too heavy and particularly disliking the lack of forward vision during landing. They liked the ruggedness of the aircraft and the firepower but the advantages were outweighed by the disadvantages.
As the need for a second fighter dissipated by the successful introduction of the Hellcat into service the trails were abandoned in April 1944. At this time 20 FR-1 Seabolts were delivered.
Republic proposed a FR-2 variant of the Seabolt based on the bubbletop P-47N in 1944 but the Navy was no longer interested.