Universal Atomic 4

The Universal Atomic 4 is a four-cylinder, gasoline engine produced by the Universal Motor Company between 1949[1] and 1984 for use as auxiliary power on sailboats.[2] Both 18 horsepower (13 kW) and 30 horsepower (22 kW) versions of the engine were produced.[3] Over 40,000 of the engines were produced during that time, with an estimated 20,000 still in use today.

A Universal Atomic 4, installed in a C&C 29 Mark 1 sailboat.

The Universal Atomic 4 was very popular in Catalina Yachts sailboats, up through 1985. Starting in the early 1970s the brand Yanmar became very popular as an auxiliary power diesel engine for sailboats, in response Universal began offering a marinized version of a Kubota diesel (tractor) engine in 1976, which was popular with sailboat manufacturers, in particular Catalina. As Yanmar diesel engines continued to gain in popularity, the Universal Atomic Four gasoline engines continued to lose market share rapidly. By 1989 Yanmar had eclipsed Universal in the diesel auxiliary market with 45% market share to 42% for Universal.

History and Lineage

The Atomic 4 is descended from an earlier Universal Motor Company design called the Utility Four,[4] which was used extensively in World War II by the United States Navy and allies to power lifeboats.[5] The Utility Four was replaced by the Atomic 4 in 1947.[6]

Applications

Specifications
Engine Type Four Cylinder, Vertical, 4 Cycle, L-Head
Bore 2 9/16" x 3 1/8"
Displacement 64.46 Cubic Inches
Compression Ratio 6.3:1
Engine Rotation Counter-clockwise from flywheel end
Firing Order 1-2-4-3 (no. 1 on flywheel end)
Reduction Gear Ratio 2.04:1 or direct 1:1 drive
Maximum Operating Angle ~15 degrees
Fuel regular leaded gasoline (will function on unleaded fuel with precautions)
Lubrication Oil SAE 30
@ RPM600100015002000250030003500
Brake Horsepower:57.311.916.2202530
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References
  1. MotorBoating. May 1981. pp. 112–. ISSN 1531-2623.
  2. MotorBoating. August 1976. pp. 49–. ISSN 1531-2623.
  3. MotorBoating. November 1965. pp. 52–. ISSN 1531-2623.
  4. MotorBoating. April 1981. pp. 134–. ISSN 1531-2623.
  5. Thomas Fleming Day (1942). The Rudder. Fawcett Publications.
  6. Stan Grayson (1 October 2008). American marine engines 1885-1950. Devereux Books. ISBN 978-1-928862-13-0.
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