On 11 April 1943, Spencer departed St. John’s in company with Task Unit 24.1.3 consisting, in addition, of Duane, two British and two Canadian escorts, and rendezvoused with the 56-ship east-bound convoy HX-233, relieving the local escort on the 12th. One straggler was reported. The convoy proceeded due east to avoid submarines reported south of Greenland and Iceland. On the 13th one escort was 25 miles to the north with four stragglers. They joined next day as did another Canadian escort. On the 15th the submarine report indicated that the convoy may have been sighted by U-boats. On the 16th Spencer dropped depth charge and delivered a mousetrap attack on a sound contact, firing eight more rounds of mousetrap ammunition on another contact an hour later. On the 17th SS Fort Rampart was reported torpedoed and Spencer screened the Canadian escort during rescue operations. At 0646 she established a contact and dropped a pattern of 10 charges and half an hour later fired mousetraps on another contact. Subsequent contacts were non-sub or lost and Spencer rejoined the convoy. At 1050 she had a sound contact and dropped 11 charges and on reestablishing it dropped 11 more. At 1117 she regained it and fired mousetraps.

At 1138 a submarine [U-175] surfaced to conning tower depth at 2,500 yards, drawing slowly right, still underway but apparently damaged. At 1140 Spencer commenced firing all guns and observed many hits on the conning tower and at its base. The crew of the submarine was observed to be abandoning ship via the conning tower. The Duane, in the immediate vicinity, assisted, firing all batteries, while merchant vessels in rear columns of the convoy opened fire on the submarine, some projectiles passing it and landing close to and on Spencer. At 1145 Spencer ceased firing and maneuvered in the vicinity of the disabled submarine. The after davit of Spencer’s No. 1 boat had been damaged by a projectile and the superstructure had been damaged by shrapnel–all of the damage was caused by friendly fire as the gunners on board many of the nearby merchant ships failed to clear Spencer while firing at the surfaced U-boat. Twenty five of Spencer’s men were injured, one dying of his wounds [RM 3/c Julius Petrella].

At 1215 Spencer lowered her No. 2 boat with a submarine boarding party. At 1220 the sub began sinking and sank stern first at 1227. At 1238 Spencer began picking up survivors alongside. The submarine boarding party returned at 1255, having boarded the submarine momentarily prior to it sinking. Three Germans were observed to be dead in the conning tower. One German officer and 18 men were rescued by Spencer and 22 by Duane.