Second patrol, November ? December 1942
On 8 November 1942, Wahoo got underway for her second war patrol, with Lieutenant Commander Dudley Walker "Mush" Morton also aboard for his prospective commanding officer (PCO) patrol. She arrived at her assigned area in the Solomon Islands, keeping Bougainville and Buka Islands in sight. On 30 November, the submarine spotted smoke at a distance of 8,000 yards (7,300 m); it was a lightly loaded freighter or transport with a destroyer escort on the port bow. Wahoo's approach was unsuccessful, and she proceeded east of Cape Hanpan.
Having patrolled the Buka-Kilinailau Channel for 17 days, on 7 December, Kennedy decided to patrol the direct route between Truk and the Shortland Islands for a few days. This proved fruitless, and Wahoo returned to her former hunting grounds, the Buka-Kilinailau Channel. On 10 December, while making her return trip, Wahoo ran across a convoy of three heavily loaded cargo ships escorted by a destroyer. She chose the largest tanker as the first target and fired a spread of four torpedoes at a range of 700 yards (640 m). Although three hit, it took two hours for Kamoi Maru (5,300 tons) to sink. The destroyer got too close and Wahoo started down before another attack could be launched. The destroyer dropped approximately 40 depth charges, none close. Rather than use the new SJ radar to mount a second attack, which might well sink the freighter, and possibly even the destroyer, Wahoo let them go on a northeasterly course and moved into a new area.
Four days later, a hospital ship was sighted headed for the Shortland Islands. Shortly after, Wahoo sunk a submarine that Kennedy identified as Japanese submarine I-15. On 15 December, Wahoo left the area and looked into Kieta Harbor, Buka Island, and passed Moreton Light on 26 December for entrance into Brisbane, Australia, where she commenced refit the following day. On 31 December 1942, Lt. Cmdr. Kennedy was relieved as commanding officer for being unproductive; he returned to surface warfare, later commanding a destroyer during the Normandy Invasion with distinction. Morton, an uncommonly talented and aggressive submarine officer, replaced him.