Abstract: A four cycle outboard internal combustion engine for driving a watercraft with a cylinder housing having cylinders arranged in at least two rows, wherein a piston is reciprocating in each cylinder, the pistons driving an approximately horizontally accommodated propeller drive shaft by way of an approximately vertically arranged crankshaft, each cylinder bank being provided with cylinder head sealing surfaces for a cylinder head housing receiving gas shuttle valves and wherein the cylinder head sealing surfaces of all of the cylinders are arranged in one single cylinder head sealing plane and an exhaust main manifold for all of the cylinders is arranged approximately parallel to the crank shaft in the cylinder head housing in the area of a central plane of the motor which is configured parallel to the crankshaft. One crankshaft is provided for each cylinder bank, the crankshafts having a stable relative speed ratio and acting upon the propeller drive shaft through a common jackshaft.