Boat propulsion machine

A boat propulsion machine that propels a boat, comprising:

• a power source;
• a drive shaft configured to be rotated by power of the power source;
• a propeller configured to generate a propulsive force for propelling the boat;
• a gear mechanism configured to transmit rotation of the drive shaft to the propeller;
• a gear case accommodating the gear mechanism and rotatably supporting the propeller;
• a tank configured to store a cooling liquid for cooling the power source;
• a heat sink configured to cool the cooling liquid;
• a cooling liquid passage connecting the power source and the heat sink such that the cooling liquid circulates between the power source and the heat sink;
• and
• a pump configured to pump the cooling liquid to circulate through the cooling liquid passage between the power source and the heat sink, wherein
• the power source, the tank, and the pump are provided at an upper portion of the boat propulsion machine,
• the gear case is provided at a lower portion of the boat propulsion machine,
• the drive shaft extends in an upper-lower direction between the power source and the gear mechanism, and
• the heat sink is provided at a position lower than the power source and higher than the gear case in the boat propulsion machine.