At 12.30 hours on 13 May 1942, the unescorted and unarmed Gulfprince (Master Peter Joseph Sigona) was steaming five miles behind of the Gulfpenn about six miles south of the Ship Shoals Sea Buoy, when the Gulfprince was attacked by U-507 in 28°32N/91°00W (grid DA 9194). The other tanker immediately left the scene at full speed, but was torpedoed and sunk by U-506 (Würdemann) at 21.38 hours the same day.

A lookout on the Gulfprince spotted the periscope one mile astern and the tanker proceeded on a zigzagging course at 10 knots. The first and second torpedo fired by U-507 at 12.38 and 13.39 hours were skillfully evaded, the first passing ahead and the second passing astern. But the third torpedo fired at 13.41 hours struck the tanker a glancing blow on the starboard side aft and abreast of the #8 main cargo tank. After glancing off, it jumped into the air about three feet and then submerged again. The collision sprung hull plates and four feet of oil leaked from the tank. The tanker continued under full steam on a zigzag course to escape. None of the eight officers and 34 crewmen on board were injured. She arrived New Orleans and went into dry dock for repairs after discharging her cargo and returned to service on 15 Jun, 1942.

The Gulfpince had been en route from Port Arthur, Texas to New York with a cargo of 71.000 bbls of crude oil. 

The Gulfprince (Master John Lund) was struck by one torpedo on the starboard side at the #7 tank. The torpedo penetrated 20 feet into the empty but non-gas-free tank before exploding. The explosion ripped a 20-foot hole in the side, destroyed the steering engine, brought down the main mast and started fires in the tanks carrying fuel. The engines were secured and the ship listed to starboard. Within minutes the complement of eight officers, 28 crewmen and 27 armed guards (the ship was armed with one 5in, one 3in and eight 20mm guns) abandoned ship in two lifeboats, three rafts and by jumping overboard. All men were picked up by the British trawler HMS Sir Gareth (T 227) and the British merchant Empire Commerce, but one of the armed guards later died from burns on board.
A salvage crew boarded the vessel and the British tugs HMS Weazel (W 120) and HMS Hudson (W 02) towed her to Algiers, arriving on 12 July.

Rather than declaring the vessel a total loss, the US War Shipping Administration bought her and chartered the tanker to the US Navy for use as a mobile storehouse in North Africa. In March 1945, the tanker was laid up at Taranto and was sold to Italy on 20 Feb, 1948 for scrapping.