Abstract: A closed loop fluid cooling system for marine motors is described. The system includes a motor cooling circuit in fluidic communication with fluid cooling jackets about a motor. The system includes a heat dissipation circuit. The motor cooling circuit is in closed fluidic communication with the heat dissipation circuit. A cooling fluid variably circulates between the motor cooling circuit and the heat dissipation circuit. A heat dissipation member is in fluidic communication with the heat dissipation circuit to receive the circulating cooling fluid, and the heat dissipation member is submerged in the body of water in which the boat is traveling to transfer heat from the cooling fluid to the body of water. A temperature control valve is in fluidic communication with the motor cooling circuit and the heat dissipation circuit.