Lycoming O-145

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Lycoming O-145 B2.jpg
Preserved Lycoming O-145
Type Piston aero-engine
National origin United States
Manufacturer Lycoming Engines

The Lycoming O-145 is a family of small, low-horsepower, four-cylinder, air-cooled horizontally opposed aircraft engine produced from 1938 until the late 1940s by Lycoming Engines. The family includes the reduction-geared GO-145.[1][2][3]

Design and development[edit]

The O-145 was produced in three major versions, the O-145-A rated at 55 hp (41 kW), the -B rated at 65 hp (48 kW), and -C rated at 75 hp (56 kW). The "B" model was the major production model, with the "A" and "C" produced in much smaller quantities.[1][2]

All models of the series had the same bore, stroke, and displacement, additional horsepower being generated by increasing compression ratio and maximum rpm. All use a Stromberg NA-S2 or NA-S2A or Marvel MA-2 or MA-2-A carburetor. The dual ignition versions use two Scintilla SF-4L, SN4LN-20 or -21, Superior SMA-4 or Edison-Splitdorf RMA-4 magnetos.[1][2]

The original O-145-A produced 55 hp (41 kW) at 2300 rpm, weighed 165.5 lb (75 kg), and featured single ignition. In an attempt to compete with the Continental A-65, Lycoming boosted the rpm and power output to 65 hp (48 kW) at 2550 rpm, and finally 75 hp (56 kW) at 3100 rpm. The O-145 had a hard time competing with the same horsepower Continentals due to its smaller displacement, which resulted in a steeper torque curve.[1][3]

The GO-145 is a geared model, introduced in 1938, that uses a 27:17 reduction ratio (1.59:1) gearbox to produce 75 hp (56 kW) at 3200 crankshaft rpm, giving 2013 propeller rpm. The engine employs a gearbox bolted to the front of the engine and the resulting engine weighs 193 lb (88 kg) without starter or generator. The GO-145 suffered from a poor reputation for reliability, because pilots mis-handled the engine, running it at too low a cruising rpm and causing gearbox wear as a result.[1][2][3][4]

The series' type certificate expired on 2 November 1950 and no O-145-B1 or -C1 or GO-145-C1s engines produced after 1 August 1941 and O-145-B2, -B3 or -C2, or GO-145-C2 or -C3s produced after 24 August 1949 are eligible for certification. The single ignition O-145-A series, O-145-B1, and -C1 are not covered by the original type certificate.[1]

Lycoming ended production of the O-145 and replaced it with the O-235 series.[3]


Four-cylinder, direct drive, 55 hp (41 kW), single ignition[2]
Four-cylinder, direct drive, 55 hp (41 kW), single ignition, with starter and generator installed[3]
Four-cylinder, direct drive, 65 hp (48 kW), single ignition[1]
Four-cylinder, direct drive, 65 hp (48 kW), dual ignition[1]
Four-cylinder, direct drive, 65 hp (48 kW), dual ignition[1]
Four-cylinder, direct drive, 75 hp (56 kW), single ignition[1]
Four-cylinder, direct drive, 75 hp (56 kW), dual ignition[1]
Four-cylinder, reduction gearbox, 75 hp (56 kW), single ignition[1]
Four-cylinder, reduction gearbox, 75 hp (56 kW), dual ignition[1]
Four-cylinder, reduction gearbox, 75 hp (56 kW), dual ignition[1]



Specifications (GO-145-C2)[edit]

Data from Type Certificate 210[1]

General characteristics

  • Type: Four-cylinder, reduction-geared engine
  • Bore: 3.625 in (92 mm)
  • Stroke: 3.500 in (89 mm)
  • Displacement: 144.5 in³ (2.4 L)
  • Dry weight: 193 lb (87.5 kg)


  • Fuel system: Stromberg NA-S2 or NA-S2A or Marvel MA-2 or MA-2-A carburetor
  • Fuel type: minimum 73 octane
  • Cooling system: air-cooled


See also[edit]

Comparable engines
Related lists


  1. ^ a b c d e f g h i j k l m n o Federal Aviation Administration (August 1949). "Approved Type Certificate 210". Retrieved 2008-12-21. 
  2. ^ a b c d e Christy, Joe: Engines for Homebuilt Aircraft & Ultralights, pages 64-65 TAB Books, 1983. ISBN 0-8306-2347-7
  3. ^ a b c d e f g h i Boggs, Jerry (n.d.). "Super KR-1". Retrieved 2008-12-21. 
  4. ^ Rotor & Wing (January 2005). "Lycoming Engines". Retrieved 2008-12-21.