Development of Four-stroke Outboard Motor

The purpose of this paper is to describe some technical features of a new type 4-stroke outboard motor, the DF250.

This model is a 4-stroke V6 outboard motor, and has the largest displacement 3,614cc and the highest maximum power 250 ps in the marketplace. The model possesses a number of remarkable features of compact engine layout, maximum output power 250 ps, high-flat torque from low to high engine revolution, and low vibration:

1. 1)
   In order to make the engine compact, the following are adopted: V-bank angle of 55 degrees, twin throttle bodies, offset driveshaft system and two-stage camshaft drive system.
2. 2)
   The following systems apply to this model to achieve both high output power and high-flat torque:
   • Continuously variable valve timing system (VVT)
   • Variable air intake pipe length system
3. 3)
   To reduce vibration, the offset driveshaft system is adopted.