At Norfolk Naval Base in the opening months of World War II, Lieutenant John W. Harkness (Cooper), a newly commissioned officer, bids goodbye to wife Ellie (Jane Greer) and reports aboard the PC-1168 unaware that his civilian background in engineering and his Rutgers education has elected him, by means of a hole punched in an IBM card, to head a secret project and command the ship. The Navy has installed a steam engine and an experimental evaporator-condenser in the ship to test its feasibility in patrol craft and has assigned Harkness to conduct the sea trials.
The crew of the submarine chaser assume that Harkness is Regular Navy. Her chief boatswain's mate, Chief Larrabee (Millard Mitchell), and her chief machinist's mate are the only experienced seamen aboard. PC-1168's crew are all newly inducted civilians, and her officers recently commissioned "90 day wonders". The exec, Lt. (j.g.) Barron (Eddie Albert), is a good-natured idea-man whose knowledge of seamanship is out of books. The engineering officer, Ens. Barbo (Jack Webb), has no training, education, or experience in engineering. And the supply-Mess officer, Ens. Dorrance (Richard Erdman), is plagued by seasickness.
After badly damaging the bow of the ship their first time underway, Harkness and his officers butt heads with gruff Commander Reynolds (John McIntire), who oversees the project as the representative of Rear Admiral Tennant (Ray Collins). The first trial results in the ship being towed into port, disparaged as the "USS Teakettle" by the rest of the base. Reynolds restricts the crew to the ship until they make the system work, and as the failures mount, the crew's morale plummets, threatening the entire project. Ellie, who is with the WAVES, gets information to her husband about Tennant's activities.
The officers hit upon a scheme to enter a crewman in the base boxing championship to unite the crew. They train an engine room sailor, Wascylewski (Charles Bronson), to represent the ship. The crew bets heavily on their shipmate, and to ensure that the "Teakettle" does not fail a sea trial scheduled for the day of the fight, smuggles distilled water aboard. Wascylewski breaks his ribs during the sea trial, forcing Barbo to stand in, but surprisingly he wins the championship.
The film climaxes with the Official Sea Trial of the "Teakettle" in which the crew improvises a successful run. Even so, the trial ends in humiliation for the crew when the ship rams an aircraft carrier—again. At the board of inquiry that follows, Admiral Tennant reveals to Harkness that the selection of his crew was no fluke: the Navy already knew that experts could run the system; it needed to see if novice sailors, who made up the overwhelming percentage of the wartime Navy, could quickly learn to operate it.Gary Cooper - Lieutenant John Harkness
Jane Greer - Ensign Ellie Harkness
Millard Mitchell - Chief George Larrabee
Eddie Albert - Lieutenant (j.g.) Bill Barron
John McIntire - Commander W.R. Reynolds
Ray Collins - Rear Admiral L.E. Tennant
Jack Webb - Ensign Tony Barbo
Richard Erdman - Ensign Chuck Dorrance
Charles Bronson - Wascylewski
Harry Von Zell - Captain Danny Eliot
Ed Begley - Port commander
Harvey Lembeck - Seaman Norelli
Lee Marvin - signalman
Jack Warden - Helmsman Morris
You're in the Navy Now was filmed in black-and-white in 1950 on location at the Norfolk Naval Yard, Hampton Roads, Virginia, and aboard the PC-1168 based there. Except for stock footage of a boxing match, verisimilitude in the film was high. Aside from PC-1168, ships that appeared prominently in the film were USS Luzon (ARG-2), USS Albemarle (AV-5), USS Marquette (AKA-95), USS Fremont (APA-44), USS Chilton, USS Roanoke (CL-145), USS Perry (DD-844),USS Vulcan (AR-5) and USS Mattabesset (AOG-52). With the exception of the Albemarle, all (including PC-1168) were anachronistic to the date of the storyline.
The film marked the screen debuts of Lee Marvin, Charles Bronson, Harvey Lembeck, and Jack Warden. U.S.S. Teakettle premiered at the Roxy Theater in New York City on February 23, 1951.