PT-491 was an 80-foot Elco from the Elco Works at Bayonne: about 56 tons, three Packard gasoline engines, roughly 40 knots, and a crew of about 14 to 17. The crew called her Devil's Daughter. She was placed in service on 2 December 1943 in Motor Torpedo Boat Squadron 33.
On the night of 24-25 October 1944 Lieutenant (junior grade) Harley A. Thronson had her in Lieutenant (junior grade) John M. McElfresh's section, with PT-490 and PT-493, in the middle of Surigao Strait. The boats were among 39 under Commander Selman S. Bowling.
In a rain squall she closed to about 700 yards on a cruiser and three destroyers and fired two torpedoes at the second ship before the enemy opened fire. She was not hit. She stayed on patrol. At 0530 she sighted the damaged Mogami steaming south, fired two more torpedoes, and withdrew behind smoke along the Panaon coast. Both missed. Mogami, which Lieutenant (junior grade) Isadore Michael Kovar reported had worked back up to 12 or 14 knots, drove PT-137 off with her secondary guns at the same time. Thronson then found the beached PT-493 and took off her survivors.
She was placed out of service on 24 October 1945. She was not sunk in the battle.