The Continental O-300 is an air-cooled, horizontally opposed six-cylinder aircraft engine rated at 145 hp at 2,700 rpm. It belongs to the same certified family as the earlier C145. The O-300-A was added to the type certificate in May 1954, followed by further versions through the O-300-E in 1963.[1]
Mechanical characteristics
Displacement is 301 cubic inches and compression ratio is 7.0:1. A Marvel-Schebler MA-3SPA carburettor supplies the mixture, and dual magnetos provide ignition. The O-300 crankshaft incorporates fifth- and sixth-order dampers. These details reflect an engine whose later development concentrated on installation features as well as the underlying six-cylinder mechanism.[1]
Variant development
The A retained the C145-2's basic arrangement with changes in materials and ignition components. The B added provision for hydraulic propeller control, and the C changed the propeller flange. The D introduced a right-angle automatic starter arrangement incorporating a vacuum-pump drive. The E added a governor mounting pad and oil supply provisions for the propeller.[1]
Aircraft use
New Zealand's type-acceptance record lists O-300-A, B, C and D engines across the early Cessna 172 series, from the original model through the 172H. These aircraft paired the engine with approved McCauley or Sensenich propellers and carried four seats.[2]
The engine also served the original Maule M-4. EASA identifies O-300-A or B engines in that high-wing, tailwheel aircraft, with a 2,700 rpm operating limit and fixed-pitch McCauley propeller options.[3]
British manufacture
Rolls-Royce manufactured the O-300D under Continental licence in Derby. The Science Museum preserves a British-built example dated 1960–1965 and identifies the Cessna 172 as a typical application. The preserved engine documents the family's production on both sides of the Atlantic.[4]