Abstract

A sixty degree, V-6 engine for an outboard motor includes loop scavenging and charging with a pair of oppositely located input passageways with differently angles sidewalls and which provide progressive, smooth constriction to the charging port to establish a highly effective velocity pattern across the top of a flat piston. Cast "Blister" cylinder liners with integral ports are integrally cast into an aluminum block. The block is cast with a single manifold between the two cylinder blanks. A milling cutter is located within the manifold to open the exhaust passageways. A T-shaped manifold is secured to close the manifold and define a pair of separate exhaust passageways. The cylinders are rotated to align the upper and lower inlet ports and particularly to locate the exhaust port projecting downwardly into a center manifold. Adjacent piston rods are mounted upon a common crankshaft pin. In high speed racing outboards the engine is fired with an inverse firing order from the lowermost to the uppermost cylinder.