Continental O-300 engine installation in a Cessna 172
The C-145 was developed from the 125 hp (93 kW) C125 engine. Both powerplants share the same crankcase, although the C145 produces an additional 20 hp (15 kW) through a longer piston stroke, higher compression ratio of 7.0:1 and different carburetor jetting.
The O-300 is a modernized C145 and retains the same weight, dimensions, bore, stroke, compression ratio, displacement and output power of the earlier engine.
The GO-300 employs a reduction gearbox, so that the engine turns at 3200 rpm to produce a propeller rpm of 2400. The GO-300 produces 175 hp (130 kW) whereas the ungeared O-300 produces 145 hp (108 kW).
The GO-300 engine has a TBO (Time Between Overhaul) of only 1200 hours, while 1800 hours is the standard for ungeared O-300 engines. The GO-300 engine also suffered reliability problems as a result of pilots mishandling the engine and operating it at too low an engine rpm. This caused the Cessna Skylark to develop a poor reputation for engine reliability. Many Skylarks flying today have been converted to different larger displacement direct drive engines.