Between 06.04 and 06.11 hours on 9 March 1943, U-510 fired torpedoes during a second attack at convoy BT-6 about 175 miles north of Cayenne, French Guiana and reported again four ships sunk. The convoy became unorganized after the first attack because all ships performed evasive maneuvers. In fact, the Mark Hanna and James Smith were damaged and the Thomas Ruffin and James K. Polk were damaged and later declared a total loss.

The Thomas Ruffin (Master Severin Broadwick) in station #31 was struck on the port side in the engine room by one torpedo that had been spotted by a lookout just before it hit. The explosion destroyed the shaft and engines, killed three men on watch below, ruptured steam lines and fuel tanks, disabled the radio and caused a list to starboard. Most of the eight officers, 35 crewmen and 15 armed guards (the ship was armed with one 4in, one 3in, four 20mm and two .30cal guns) on board abandoned ship in two lifeboats and two rafts. The commander of the armed guards and one crewman remained on board and were joined by the master and one crewman who reboarded the ship at daylight. 40 survivors were picked up by USS Courage (PG 70), but three of them died from steam burns and 15 were transferred to USS Borie (DD 215) before all were landed at Trinidad on 13 March. In all, two officers, two crewmen and two armed guards were lost. At 15.30 hours on 9 March, USS PC-592 took off the four men from the Thomas Ruffin which was towed by HMS Milford (U 51) (LtCdr G. MacClelland, RN) to the naval dock in Port of Spain, arriving on 17 March. After some repairs she was towed to Mobile and declared a total loss. Broken up at Mobile in 1946.

The master Severin Broadwick already lost two other ships to U-boats when Mary was sunk by U-129 (Clausen) on 3 March 1942 and George Calvert was sunk by U-753 (von Mannstein) on 20 May 1942.