[2] For surface running, the boats were powered by two 500-brake-horsepower (373 kW) diesel engines, each driving one propeller shaft.

[5] Ro-117 got underway from Japan on 31 March 1944 along with the submarine Ro-116 for her first war patrol, ordered to intercept an Allied task force operating in the vicinity of the Palau Islands.

[5] She departed Kure, Japan, on 15 May 1944, called at Saipan in the Mariana Islands from 24 to 26 May 1944, then proceeded to Truk, which she reached on 31 May 1944.

[5] On 14 June 1944, Ro-117 received orders to proceed at flank speed to a new patrol area off the Marianas east of Guam.

[5] In the predawn darkness of 17 June 1944, Ro-117 was on the surface 350 nautical miles (650 km; 400 mi) southeast of Saipan when an Eniwetok-based United States Navy PB4Y-1 Liberator patrol bomber of Bombing Squadron 109 detected her on radar.

[5] On 12 July 1944, the Imperial Japanese Navy declared her to be presumed lost off Saipan with all 55 men on board.