The invention relates to a pod propulsion unit of a ship. The pod propulsion unit comprises a pod housing arranged at least partly below a hull of the ship, an electric propeller motor within a motor gondola of the pod housing, an annular gap between a rotor and a stator of the electric propeller motor, and gas channels extending through the rotor, a closed cooling gas circuit, and a fan for circulating gas in the closed cooling gas circuit. The closed cooling gas circuit comprising a feeding duct extending between the return duct and the first motor end face of the electrical propeller motor, and a return duct extending between the feeding duct and the opposite second motor end face of the electrical propeller motor.