A lubricating system for a four-cycle engine positioned within an engine compartment of a personal watercraft for powering a water propulsion unit thereof, is disclosed. The engine compartment, and engine therein, is accessible through a maintenance opening in deck of the watercraft. Preferably, the lubricating system includes an oil filter which is positioned at other than the bottom of the engine for access through the maintenance opening, such as at the front or rear end of the engine. In addition, the engine preferably includes an oil drain which is positioned below the oil filter for draining the oil from the engine.