A motor device for providing propulsion of a floating vessel includes an electrical motor and a propeller arrange inside a propeller house, a hollow rotatable or non-rotatable mid-section arm, a battery and controlling unit. A controlling logic for motor control is arranged inside the rotatable or non-rotatable mid-section arm. The controlling logic includes a heat conductive substrate arranged to contact the inner surface of the rotatable or non-rotatable mid-section arm in a portion of the inner circumference of the rotatable or non-rotatable mid-section arm.