An internal combustion engine has a power unit case having a crankcase, a first housing flange and a second housing flange. The crankshaft axis and the output shaft axis define a reference plane. An oil pump has an oil pump shaft, having an oil pump shaft axis, disposed at least partially in an oil pump chamber. A normal projection of the oil pump shaft axis onto the reference plane is located between the crankshaft axis and the output shaft axis. A first housing cover is mounted to the first housing flange on a first side of the power unit case. A separate oil pump cover is mounted to the second housing flange on the first side of the power unit case to close the oil pump chamber.