Jet propulsion craft provided with exhaust noise eliminating apparatus

Abstract

A jet propulsion craft propelled upon a water surface generally comprises a hull structure comprising a bottom plate and an upper plate, an engine mounted upon the bottom plate at substantially a middle portion of the hull structure as considered in the longitudinal direction thereof, the engine being provided with an exhaust port, an exhaust system extending rearwardly from the engine and provided with an inlet end and an outlet end, the inlet end being operatively connected to the engine exhaust gas discharging port, and a jet pump mounted upon the bottom plate at a rear portion of the hull structure and driven by means of the engine. An exhaust gas noise eliminating device operatively connected to the outlet end of the exhaust system is further provided for the craft for eliminating the exhaust gas noise in a stepwise manner. The exhaust gas noise eliminating device comprises a hollow guard plate mounted upon the bottom plate at the rear portion of the hull structure and the inner hollow portion thereof is divided into a plurality of expansion chambers. The exhaust gas noise eliminating device may also comprise a box like member mounted upon a rear end portion of the hull structure and the inner hollow portion thereof may be divided into a plurality of expansion chambers.