At 02.31 hours on 7 July 1944 the unescorted Esso Harrisburg (Master Ernest Chipman Kelson) was hit by a Gnat from U-516 about 200 miles northwest of Aruba. The tanker had just stopped zigzagging at 13.5 knots, when a lookout spotted the torpedo and the helmsman put the helm over hard left. She managed to turn 90° but the acoustic torpedo followed and struck under the stern. The explosion destroyed the 4in gun on the stern and damaged the rudder and screw. The ship lost headway and began to settle slightly by the stern. Ten minutes after the hit, the eight officers, 36 men and 28 armed guards (the ship was armed with one 4in, one 3in and eight 20mm guns) abandoned ship in four lifeboats and two rafts in the heavy seas. At 02.40 hours, a second torpedo struck in the cross bunkers on the starboard side, aft of the #8 tank. 15 minutes later a third torpedo struck the #6 tank on the starboard side, causing the vessel to sink within one minute.
Five survivors on a raft and 13 others in a boat were picked up by the American submarine chaser USS SC-1299 the next day and taken to Aruba The same day, the Dutch patrol vessel Queen Wilhelmina (the former American USS PC-468) picked up 31 survivors from two lifeboats. Another boat with 15 men made landfall five days later near Santa Marta, Colombia, where the were picked up by a blimp of the US Navy and taken to Barranquilla, Colombia. The master, three men and four armed guards died.

At 06.18 hours on 8 July 1944 U-516 fired a spread of three torpedoes and one Gnat on the American motor tanker Point Breeze (4756 tons) in grid EC 8263, but all torpedoes were evaded by the tanker.