Abstract: A separate lubricating system for a two-stroke-cycle outboard engine comprises a sealed oil tank disposed above the engine for storing therein a lubricating oil used in the separate lubricating system. Compressed air from a crankcase of the engine passes through a check valve attached to the crankcase and is introduced into the oil tank by a pipeline. The separate lubricating system is also provided with a plunger pump for forcibly delivering oil supplied from the oil tank under the compressive force of the compressed air to lubricated parts of the engine. The separate lubricating system of the engine can correctly meter the quantity of the lubricating oil even when air is charged into and trapped in the plunger pump.