Jet propulsion boat

Abstract

To provide a jet propulsion boat that enables preventing the occurrence of cavitation. In a jet propulsion boat that jets water pressurized and accelerated by a water jet pump from a rear jet nozzle and is propelled by its reaction, a turbocharger is provided to an engine for driving the water jet pump and in case the rate of the rise of engine speed is a predetermined value or more, delay control is applied to the rise of the boost pressure of the turbocharger.

We claim:  
     
         1 . A water jet propelled boat comprising: 
 a water jet pump that pressurizes and accelerates water from an inlet port to an outlet port;    an engine for driving the water jet pump, the engine including a power booster for compressing intake air, and a throttle for regulating the intake air flow into the engine;    a controller for regulating the power booster;    a power booster pressure sensor connected to the controller; and    an engine speed sensor connected to the controller;    wherein the controller is adapted to regulate the pressure in the power booster in response to the sensed engine speed to avoid cavitation even when the throttle is in a fully open position.    
     
     
         2 . A water jet propelled boat comprising: 
 a turbocharger;    a controller for regulating the air pressure within the turbocharger, wherein the controller includes: 
 a memory adapted to store predetermined values;  
 a throttle angle sensor for sensing throttle angle;  
 a turbocharger pressure sensor for sensing turbocharger pressure;  
 an engine speed sensor for sensing engine speed;  
 a timer for obtaining elapsed time; and  
 a processing unit for setting a target pressure in the turbocharger based upon predetermined values and sensed values of throttle angle, turbocharger pressure, engine speed, and elapsed time.  
   
     
     
         3 . The water jet propelled boat according to  claim 2 , wherein controller applies delay control to the rise of the pressure in the turbocharger when the acceleration of the engine reaches a predetermined value.  
     
     
         4 . The water jet propelled boat according to  claim 2 , wherein the controller limits the pressure in the turbocharger when the engine speed reaches a predetermined value.  
     
     
         5 . The water jet propelled boat according to  claim 3 , wherein the predetermined value is set as to avoid cavitation.  
     
     
         6 . The water jet propelled boat according to  claim 4 , wherein the predetermined value is set as to avoid cavitation.  
     
     
         7 . A water jet propelled boat comprising: 
 a water jet pump that pressurizes and accelerates water;    an engine for driving the water jet pump, the engine including a user controlled throttle for regulating the engine speed; and    means for decreasing available range of engine speeds to avoid cavitation even when the throttle is fully opened.