Four-cycle outboard motor

摘要

Embodiments of four-cycle outboard motors having an improved exhaust system. The exhaust system includes an expansion chamber that is formed in the drive shaft housing of the outboard motor below an oil tank for the engine which is positioned therein. A water chamber is formed around the expansion chamber and the lower portion of the oil tank for cooling them. An above-the-water exhaust gas discharge is provided that communicates with the area above the water jacket.