An engine assembly includes a coolant pump, an engine structure, a radiator supply feed and a radiator bypass feed. The engine structure defines a first set of cylinders, a first coolant return gallery and a first cooling jacket. The first coolant return gallery extends in a longitudinal direction from a first longitudinal end to a second longitudinal end of the engine structure. The first cooling jacket is in communication with the coolant pump and with the first coolant return gallery. The first coolant return gallery forms a radiator bypass passage providing the coolant fluid to the coolant pump and bypassing the radiator during a first operating condition and forms a radiator supply passage providing the coolant fluid to the radiator during a second operating condition.