PURPOSE: To discharge bilge water positively by utilizing an impeller rear flow in a jet propulsion machine for obtaining negative pressure of sufficient magnitude.
CONSTITUTION: A nozzle 6 whose flow passage is tapered is formed on the rear flow side of an impeller in a jet propulsion machine, and stationary blades 63 which inhibits an impeller rear flow from whirling are mounted at the tapered part of the nozzle 6. Moreover, a protrusion 65 moderately rising from the periphery in the inner surface of the nozzle 6 is formed on the rear flow side of the blades 63, and a bilge drainage port 66 which is open to the rear flow side of the protrusion 65 is also formed. In addition, a water jetting passage 67 which communicates with the bilge drainage port 66 from upstream of the protrusion 65 is formed, and a bilge drainage passage 68 which is led from a bilge suction port in a boat penetrates from the outside of the protrusion to communicate with the bilge drainage port 66.
KOYANO SATOSHI
NUMANO KAZUHIRO
