PT-40 was a sister of PT-37, another 77-foot Elco from Bayonne. She was laid down on 25 April 1941, launched on 7 July, and placed in service on 22 July with Motor Torpedo Boat Squadron 2. For a few months her papers called her PTC-20. In March she was PT-40 again. The squadron went to the Panama Sea Frontier. At the Taboga commissioning the boats wore false cabin numbers, 0 through 10, and she was number 9. Late in 1942 she was shipped to the Solomons.
Henry S. Taylor had her on 7 December, the night eight boats went out from Tulagi. He was patrolling off the northwest tip of Guadalcanal with PT-48. Two of that boat's engines quit, and the destroyers started shooting at her. Taylor swung PT-40 across so the fire would follow him. PT-48 got into the lee of Savo on one engine. His own boat was not hit.
On the night of 11–12 December he was out again, with Lester H. Gamble in PT-37. Taylor, Gamble, and Williams E. Kreiner each claimed a torpedo hit. Teruzuki sank off Savo after two torpedoes in the stern, and the hit is not pinned to PT-40. Frank Freeland's boat was burning in the same fight. In the morning Taylor took a swimmer off the beach on Savo. Two officers and seven enlisted men were lost with that boat.
Clark W. Faulkner had her on 10 January 1943, on the patrol between Cape Esperance and Aruligo. Later that month Allen H. Harris had her. He fired two torpedoes at a ship standing in toward Tassafaronga and was sure that neither hit. She came through the Solomons. On 11 November 1943 she moved to Motor Torpedo Boat Squadron 3. On 15 April 1944 she was reclassified as the small boat C73995 and laid up at Melville, where the repair school used her and put new planking on the hull. The Maritime Commission advertised her for sale in October 1946. A hull kept ashore at Kingston, New York, was still being called PT-40 in 2015.
