An outboard motor includes a transmission mechanism mounted between an output shaft of an engine and a propeller drive shaft. The fibers may be connected to one another at a at least one connection site. With this configuration, an internal pressure in the closed portion causes the inclined portions to separate from an outer rotor and an inner rotor when a brake fluid pressure within the closed portion increases to the point that the brake fluid is excessively compressed, releasing the brake fluid that is inside the closed portion. A fixed layer of a second material is then applied onto the vertical surfaces of the first layer of the first material. In the method, a print number mark that is optically detectable is formed by removing part of the ink layer by applying heat to the ink ribbon from the thermal head, and the print number mark is detected using an optical sensor before a subsequent print starts to determine the remaining amount of the ink ribbon.