The Universal Atomic 4 is a four-cylinder, 64.46 cubic inch, 30 hp 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, even multiple decades after the Universal Motor Company ceased production.

History and Lineage

The Atomic 4 is descended from an earlier Universal Motor Company design called the Utility Four, which was used extensively in World War II

World War II

World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

 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.

Specifications

Engine Type	Four Cylinder, Vertical, 4 Cycle, L-Head
Bore	2 9/16" x 3 1/8"
Displacement Engine displacement Engine displacement is the volume swept by all the pistons inside the cylinders of an internal combustion engine in a single movement from top dead centre to bottom dead centre . It is commonly specified in cubic centimeters , litres , or cubic inches...	64.46 Cubic Inches
Compression Ratio Compression ratio The 'compression ratio' of an internal-combustion engine or external combustion engine is a value that represents the ratio of the volume of its combustion chamber from its largest capacity to its smallest capacity...	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 Fuel Fuel is any material that stores energy that can later be extracted to perform mechanical work in a controlled manner. Most fuels used by humans undergo combustion, a redox reaction in which a combustible substance releases energy after it ignites and reacts with the oxygen in the air...	unleaded gasoline
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

• Moyer Marine - Parts and Services for the Universal Atomic 4 Engine

• Links to full Atomic 4 technical manual and owner's guide in .pdf format from Engines1.com

• The Care & Feeding of an Atomic 4