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The Care and Feeding of the Universal Atomic Four Engine


Possibly updated information and reader editable information

Most Alberg 30s, like most boats of the time, were delivered with Universal Atomic 4 gasoline-powered auxiliary engines. Some people have replace these with diesels, maybe because their Atomic 4 was wearing out or they were concerned about the explosion hazard of gasoline, but the Atomic 4 remains a reliable, safe, cost-effective power plant for moderate-sized auxiliary sailboats. If you make an unfailing habit of running the bilge blower for five minutes and then sniffing the outlet for fumes, you can neutralize the danger.

Still, these engines are getting older. I've been told that this block was the original engine in the Jeep. (I've also heard that they're based on an industrial stationary engine, the International Harvester Farmall Cub engine, and a Chevy.) They're not made any more and, like all of us, require a little tender loving care to keep them happy. Keep it painted to prevent rust. When we bought our boat, this precaution had not been taken. In my ignorance of marine engines, I left it that way. The cylinder head rusted through.

Switching to fresh water cooling can add years of life to your engine. Two of the endemic problems are corrosion and overheating. Both of these are caused by salt water cooling. You can imagine the damage that hot salt water can do over time to a metal casting. The salt also precipitates out in the cooling jacket, blocking the flow of water and causing the engine temperature to rise. As the engine gets hotter, the salt precipitates faster. That's the reason that salt-water engines should use a 140F thermostat. This is a bit cooler than a gasoline internal-combustion engine likes, but it will tolerate it. If you switch to fresh-water cooling, you can install a 170F and enjoy better combustion.

General Specifications

Model Designation UJ, UJR
Engine Type Four Cylinder, Vertical, 4 Cycle, L-Head
Bore and Stroke 2 9/16" x 3 1/8"
Total Piston Displacement 64.46
Compression Ratio 6.3:1
Engine Rotation Counter-Clockwise (From Flywheel end)
Firing Order No. 1 on Flywheel End 1-2-4-3
Reduction Gear Ratio 2.04:1
Maximum Operating Angle Approximately 15 degrees
Fuel Regular Grade 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

Suggested Oil LevelsAngle of Install'nAmount FullAmount Low
(Quarts) 0 degrees 5.75 5
5 degrees 4.75 4
10 degrees 3.5 2.75
14 degrees 2.75 2.25


Boatowners Mechanical And Electrical Manual book cover Boatowners Mechanical And Electrical Manual by Nigel Calder

An in-depth reference to almost every essential system found on a sailboat. Calder has well-considered strategies for everything. Granted, there are good alternatives to some of his approaches, but he won't lead you astray. This is a book you can trust. Now expanded in its second edition.

Other books by Nigel Calder



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