An outboard motor having a multi-cylinder four-cycle, internal combustion engine as a power plant. The engine is provided with an oil reservoir in the upper portion of the drive shaft housing and lower unit. Oil is drained back to this oil reservoir by separate drain passages formed in the cylinder head and in the crankcase. In addition, an improved crankcase ventilating system is provided wherein the crankcase ventilating gases follow a circuitous path through the crankcase chamber, camshaft chambers and then to the intake system so as to reduce the emissions of hydrocarbons.