Development of Four-stroke Outboard Motor 2001-01-1803

Suzuki Motor Corporation has developed a new four-stroke outboard motor series, “DF90/115”. It is an inline 4 cylinder, DOHC 16-valve engine. The DF115 version delivers a maximum power output of 84.6 kW (115 PS).

The motor features not only lower noise, vibration and fuel consumption than a comparable two-stroke model, but also lower emissions conforming to CARB (California Air Resources Board) 2008 requirements. Moreover, the size and weight of the DF90/115 have been significantly reduced by adopting an offset driveshaft system and a 2-stage camshaft drive system. Thus the DF90/115's side profile is the smallest among four-stroke outboard motors in the 85 kW class. Furthermore, the new motor offers a propulsion performance equivalent to the two-stroke outboard motor, due to the development of a large high-performance propeller based on a large reduction gear ratio and a 4-2-1 exhaust system. This paper reports the technologies, modal analysis and structural dynamics modifications techniques used in developing the DF90/115.