Abstract: A marine Diesel engine consists of parallel left and right engines mounted on a common bed plate having integral independent columns on which the cylinders of the engine are supported, the bed plate and columns forming the crank chambers of the engines. The exhaust and scavenging pipes for the engines are constructed as common parts, the scavenging pipe being mounted between the engines and being flexibly connected to at least one of them so as to permit relative movement between the engine upper portions. A single propeller shaft is driven at a desired low r.p.m. from the crank shafts of the engines through a gearing device consisting simply of a gear on the propeller shaft meshing with a pair of pinions each connected to one of the engine crank shafts by an elastic coupling.