Propulsion system for boats

A propulsion system for boats, wherein:

• a propelling machine is configured curved- tubular, on a ship bottom, with a front casing having a suction inlet opening fore to water, an impeller casing having an impeller inscribed thereto, and a rear casing having a delivery outlet opening aft to water;
• and
• the impeller inscribed to the impeller casing is forward and reverse rotatable;
• wherein the impeller casing, and the front casing and the rear casing, connected to front and rear ends of the impeller casing, respectively, have flow paths therein substantially identical in size to an inside diameter;
• and
• wherein the impeller casing is separable into an upper half of the impeller casing and a rear half of the impeller casing;
• and
• a drive shaft is supported by the upper half of the impeller casing.