S-43 was launched 31 March 1923, at the Quincy, Massachusetts yard of the Bethlehem Shipbuilding Corp. She was commissioned on 31 December 1924, under the command of Lieutenant C.E. Braine, Jr.
Assigned to SubDiv 19, and then to SubDiv 11, S-43 completed her trials and in April 1925 proceeded to the Submarine Base at Coco Solo, in the Panama Canal Zone, via Quantanamo Bay. She remained at Coco Solo for the next two years. In 1927, her Division was moved to San Diego.
In 1930, S-43 was reassigned to Pearl Harbor, where she remained, except for periods of inactivity with the rotating reserve between 1932-35.
Morton C. Mumma, Jr., took command of S-42 in the summer of 1935, remaining in command until 1938. At the time Mumma took command, S-43 was still homeported at Pearl Harbor, but the entire Division was moved to Coco Solo, in the Panama Canal Zone, in the Spring of 1936, where she would remain through the end of Mumma’s time in command.
Lieutenant Commander Mumma would go on to recommission the salvaged U.S.S. Sailfish (SS-192), the former U.S.S. Squalus., in May 1940, and would command her during her first war patrol.
SubDiv 11 was moved to New London, where it was redesignated SubDiv 53. The old S-boats were then rotated in groups to Philadelphia, where they were overhauled and updated in preparation for possible war duty, as by that time the only issue really in doubt was when the United States would be drawn into World War II.
Putting to sea in August 1941, S-43 suffered a complete power failure. In September, her problems repaired, she took up patrol and training duties out of Bermuda. At the end of October, she returned to the United States, operating out of the New London-Newport area, moving north to Newfoundland in November to test the effects on S-boat operations in extreme winter conditions.
At the outbreak of war, S-43 departed Canada, returning to New London, then continued on to Coco Solo. She reached the Canal Zone on 27 December, transiting the Canal on 9 January 1942 to conduct a security patrol in the Pacific approaches. She returned to Coco Solo on 2 February to prepare for transfer to Australia with her division.
On 5 March 1942, SubDiv 53, in company with Griffin, departed for Australia. In mid-April the division arrived in Brisbane, joining the Asiatic Fleet’s S-boats to form Task Force 42.
S-43 set off on her first war patrol on 11 May 1942. After passing 15° south she ran submerged during the day—a far from comfortable proposition in an un-air-conditioned S-boat.
Arriving on station in the St. George’s Channel, between New Ireland and New Britain, on the 21st. Problems started three days later when both main engine air compressors broke down. As submarine diesels use compressed air for starting, and compressed air is also needed for surfacing, this presented a major problem, for the only available air for either purpose was that which was already stored in the air banks.
The crew managed to repair the starboard compressor, but the port unit was to remain unusable for the rest of the patrol. Further problems developed due to leaks in sea valves, contaminated fuel oil, and a problem with fogging in the number 1 periscope.
Between 26 May and 1 June, S-43 ran submerged during the day, surfacing at night to charge batteries. Surfacing on the 2nd, she ran on one engine, arriving in Brisbane on 10 June.
Taken into dock for repair and refit, S-43 departed Brisbane on 8 July for the Bismarck Archipelago. Aboard was Flight Officer C.F. Mason, of the Royal Australian Air Force, liaison and rescue officer for Allied agents on New Ireland and Feni Island. He was put ashore on New Ireland on the night of the 19th. She picked him up the next night, but he had been unable to contact his agent.
On the night of 21 July, S-43 put Mason ashore on Feni Island. His mission was to bring off the agent stationed there. Mason sent a message to S-43 to send a boat, his inflatable having been damaged. Another boat was sent, bringing off Mason, but not the agent. Mason went ashore again on the 23rd. The following night he failed to answer S-43‘s signals, nor did he respond to additional communication attempts.
Being reluctantly forced to conclude, after numerous attempts to make contact, that Mason and his agent had been captured by the Japanese, S-43 returned to Brisbane, arriving on 7 August.
Scheduled for a 27 August 1942 departure on her third war patrol, problems with the main engines postponed the start of the patrol to 14 September. Initially sent to intercept Japanese shipping headed for Milne Bay by patrolling east of Kiriwina in the Trorbriand Islands, S-43 was then sent to the Buka Island area in the Solomon Islands. No worthwhile targets were sighted and S-43 returned to Brisbane on 14 October.
SubDiv 53 got under way as a group on 4 November, bound for Coco Solo on the Atlantic end of the Panama Canal in company with Griffin, arriving on 9 January 1943. Remaining in the Canal Zone until early April, S-43 was sent briefly to Cuba, then returned to Panama, transiting the Canal and arriving in San Diego on 26 April. There she operated with the West Coast Sound School through the summer.
In September, she began a five-month overhaul in preparation for a return to active service in the Solomons. Proceeding to Pearl Harbor in February 1944, she remained there until the following month dealing with still more engine problems. Under way on 31 March, her voyage was interupted by a crankcase explosion on 4 April. As a result, S-43 put into Espritu Santo for more repairs.
She finally arrived in Purvis Bay on 22 April. From there, she participated in anti-submarine warfare training with Allied air and surface units. She moved to Australia in January 1945, where she continued the same duties through February.
Departing for for home on 2 March, S-43 continued her run of less than perfect luck when she was fired on by a “friendly” merchantman on the 18th. She submerged before any damage was done, and reached San Diego on 5 April.
Sent to San Francisco after the Japanese surrender, S-43 was decommission on 10 October 1945. She was stricken on 13 November and sold for scrap in 1946.
Sponsor: Mrs. J.H. Brown
First Captain: Lt. C.E. Braine, Jr
Stricken/Lost: Scrapped 1945