The Universal Atomic 4 is a four-cylinder, gasoline engine produced by the Universal Motor Company between 1949 and 1984 for use as auxiliary power on sailboats. Both 18 horsepower (13 kW) and 30 horsepower (22 kW) versions of the engine were produced. Over 40,000 of the engines were produced during that time, with an estimated 20,000 still in use today.