At 00.33 hours on 22 Nov 1942 the unescorted Alcoa Pathfinder (Master Frederick Ferdinand Dumke) was struck by a torpedo on the port side abreast of the engine room. U-181 had spotted the ship silhouetted by full moon about 75 miles south of Lourenço Marques, Mozambique. The explosion blew debris nearly 200 feet into the air. The cargo caused the ship to sink by the stern within three minutes, still under way with four knots. Five armed guards remained at the after 5in gun (she was also armed with four 20mm and two .30cal guns) until the last minute, but they were unable to fire because they never spotted the U-boat and had to jump overboard. The most of the ten officers, 35 men, 15 armed guards and one passenger got away in one lifeboat and two rafts. But one officer and two men died on watch below, the passenger and one crew member failed to leave the ship and the radio operator died from electrical shock trying to send distress signals. 18 hours after the attack, the survivors landed about 23 miles north of Point Oro Light. They then walked about 25 miles, led by Zulu guides and camped for the night in a cabin. The next day they were taken to Maputo airfield. On 25 November, they were flown to Durban and eventually repatriated to USA.

U-181 was informed of the sailing times of the Alcoa Pathfinder, East Indian and Excello from a secret transmitter located aboard the German motor merchant Ehrenfels which was interned along with the German motor merchants Braunfels and Drachenfels and the Italian steam merchant Anfora in the Portuguese Mormugao Harbor. The information was given to the ship by a German spy living in Goa. On 9 March 1943 the Ehrenfels was scuttled by the own crew to prevent seizure by Portuguese.