<P> The most successful early outboard motor, was created by Norwegian - American inventor Ole Evinrude in 1909 . Between 1909 and 1912, Evinrude made thousands of his outboards and the three horse units were sold around the world . His Evinrude Outboard Co. was spun off to other owners, and he went on to success after starting the ELTO company to produce a two - cylinder motor - ELTO stood for Evinrude Light Twin Outboard . The 1920s were the first high - water mark for the outboard with Evinrude, Johnson, ELTO, Atwater Lockwood and dozens of other makers in the field . </P> <P> Historically, a majority of outboards have been two - stroke powerheads fitted with a carburetor due to the design's inherent simplicity, reliability, low cost and light weight . Drawbacks include increased pollution, due to the high volume of unburned gasoline and oil in their exhaust, and louder noise . </P> <P> Although four stroke outboards have been sold since the late 1920s, particularly Roness and Sharland, in 1962 Homelite introduced a commercially viable four cycle outboard a 55 - horsepower motor, based on the 4 cylinder Crosley automobile engine . This was called the Bearcat that was later purchased by Fischer - Pierce who are the makers of Boston Whaler for use in their boats because of their technical superiority and efficiency over two strokes . In 1964, Honda Motor Co. introduced its first four - stroke powerhead . In 1984, Yamaha introduced their first four - stroke powerhead . These motors were only available in the smaller horsepower range . In 1990 Honda released 35 hp and 45 hp four - stroke models . They continued to lead in the development of four - stroke engines throughout the 1990s as US and European exhaust emissions regulations such as CARB (California Air Resources Board) led to the proliferation of four - stroke outboards . At first, North American manufacturers such as Mercury and OMC used engine technology from Japanese manufacturers such as Yamaha and Suzuki until they were able to develop their own four - stroke engine . The inherent advantages of four - stroke motors included: lower pollution (especially oil in the water), noise reduction, increase fuel economy, increased low end torque, and smoother operation . </P> <P> Honda Marine Group, Mercury Marine, Mercury Racing, Nissan Marine, Suzuki Marine, Tohatsu Outboards, Yamaha Marine, and China Oshen - Hyfong marine have all developed new four - stroke engines . Some are carburetted, usually the smaller engines . The balance are electronically fuel - injected . Depending on the manufacturer, newer engines benefit from advanced technology such as multiple valves per cylinder, variable camshaft timing (Honda's VTEC), boosted low end torque (Honda's BLAST), 3 - way cooling systems, and closed loop fuel injection . Mercury Verado four - strokes are unique in that they are supercharged . </P>

When did yamaha start making 4 stroke outboard motors