US Patent 7494391 Propulsion unit for outboard motor

A lubricant circulating system has a lubricant passage formed in a propeller shaft. The lubricant passage extends axially along the propeller shaft from a bevel gear mechanism to a position proximate to a journal of the propeller shaft. The journal of the propeller shaft is rotatably supported by a bearing. The lubricant passage further extends radially of the propeller shaft and communicates with an area proximate to the bearing. The lubricant circulating system is adapted such that lubricant circulates through the lubricant passage between an upstream opening of the lubricant passage at or around the bevel gear mechanism and a downstream opening of the lubricant passage in the vicinity of the bearing.