Snowmobile

A snowmobile, comprising:

• a frame having a tunnel;
• a seat configured to be supported on the tunnel;
• an engine supported by the frame;
• an endless belt assembly supported by the frame;
• the tunnel including first and second longitudinally spaced-apart ends and extending above the endless belt assembly, the tunnel having a center panel and side panels, the center panel having an inlet and an outlet defined therethrough;
• and
• a lower panel is coupled to a bottom side of the center panel such that the lower panel and the center panel together define an integral heat exchanger adapted to receive a coolant from the engine, wherein a lower surface of the center panel defines an upper wall of the heat exchanger and an upper surface of the center panel is exposed to an external environment, and the lower panel defining a fluid pathway having a first channel in fluid communication with the inlet and a second channel in fluid communication with the outlet.