Abstract: An opposed piston engine includes at least one cylinder with a bore surface and longitudinally-spaced exhaust and intake ports that open through the sidewall of the cylinder. A pair of opposed pistons is disposed in the cylinder for sliding movement along the bore surface. An oil-retaining surface texture pattern in an interface between the pistons and the bore surface extends in a longitudinal direction of the cylinder, aligned with bridges of at least one port. The surface texture pattern includes a plurality of separate recesses on an outside surface of a skirt of each piston. Alternatively, or in addition, the surface texture pattern includes a plurality of separate recesses extending in a longitudinal direction of the cylinder, aligned with bridges of at least one port.

Abstract: An opposed piston engine includes at least one cylinder with a bore surface and longitudinally-spaced exhaust and intake ports that open through the sidewall of the cylinder. A pair of opposed pistons is disposed in the cylinder for sliding movement along the bore surface. An oil-retaining surface texture pattern in an interface between the pistons and the bore surface extends in a longitudinal direction of the cylinder, aligned with bridges of at least one port. The surface texture pattern includes a plurality of separate recesses on an outside surface of a skirt of each piston. Alternatively, or in addition, the surface texture pattern includes a plurality of separate recesses extending in a longitudinal direction of the cylinder, aligned with bridges of at least one port.

Abstract: A four-cycle internal combustion engine is provided with a scavenge pump and a pressure pump that are both attached for rotation to a crank shaft of the engine. The inlets and outlets of the scavenge pump and pressure pump are located at positions within the structure of the internal combustion engine which inhibits the drainage of lubricant from a lubricant reservoir to the engine when the outboard motor is either tilted at an extreme angle from vertical or stored in a horizontal position. The scavenge pump and the pressure pump can be gerotor pumps and can either be located proximate each other at one side of the engine or displaced from each other on opposite sides of the engine.

Abstract: A cooling system for an internal combustion engine is provided with coolant paths through the cylinder block and cylinder head which are connected in serial fluid communication with each other. In parallel with the cooling path through the cylinder head, a first drain is connected in serial fluid communication with a pressure responsive valve and the path through the cylinder block. A temperature responsive valve 64 is connected in serial fluid communication with the cylinder head path and in parallel fluid communication with the first drain. A pump is provided to induce fluid flow through the first and second coolant conduits and the first and second drains, depending on the space of the pressure responsive valve and the temperature responsive valve.

Abstract: In a two-cycle internal combustion engine (10), the piston (20) has an outer peripheral oval shape (58) with a minor axis (62) offset from the centerline (54) of the wrist pin (26) towards a line (56) through the intake and exhaust ports (16 and 18). The outer peripheral shape of the piston also has increasing ovality, from at least the wrist pin (26) upwardly to at least the piston rings (22, 24).