To prevent breakage of an impeller shaft by wetting all peripheries and all surfaces of a normal seal ring by supplying cooling water even when an impeller shaft of a water jet propulsion device has a non-submerged part in detaining a vessel.

This seal structure of the impeller shaft of the water jet propulsion device to seal the impeller shaft with the front normal seal ring and a rear emergency seal body stored in a seal housing provided in the middle by extending the impeller shaft to drive an impeller arranged in an intake duct formed on a hull forward with a space in a protective pipe provided in the inside of the hull constitutes its characteristic feature of providing a filler hole to fill cooling water to cool the normal seal ring on the seal housing and communicating an upper part of the seal housing and the space in the protective pipe in the rear of the emergency seal body through to each other with a downtake pipe.

COPYRIGHT: (C)2007,JPO&INPIT