Universal Atomic 4

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The Universal Atomic 4 is a four-cylinder, 64.46 cubic inch, 30 horsepower (22 kW) gas engine produced by the Universal Motor Company between 1947 and 1984 for use as auxiliary power on sailboats. Over 40,000 of the engines were produced during that time, with an estimated 20,000 still in use today. This "workhorse" engine dominated the expanding sailboat market starting in the 1960s, and between the years of 1965 and 1975 they were installed on up to 80% of new sailboats in the 25-40 foot (7.6-12 meter) range. Their longevity and reliability is proven by the fact that thousands of sailors still depend on the engine.

History and Lineage[edit]

The Atomic 4 is descended from an earlier Universal Motor Company design called the Utility Four, which was used extensively in World War II by the United States Navy and allies to power the lifeboats for the ships, barges, and tankers of many navies and merchant marine fleets. The Utility Four was replaced by the Atomic 4 in 1947.


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
@ RPM 600 1000 1500 2000 2500 3000 3500
Brake Horsepower: 5 7.3 11.9 16.2 20 25 30

External links[edit]