Boat propulsion device

A vessel propulsion system, comprising:

• a suction casing configured with a suction inlet opening at a bottom of a hull of a vessel, a suction flow path ascending from the suction inlet, and an impeller chamber substantially horizontal in position, and disposed at a bottom part of a stem of the hull;
• a delivery casing connected to the suction casing and submerged under a draft of the hull;
• a combination of front and rear impellers provided inside the impeller chamber of the suction casing;
• a combination of first and second drive shafts provided through the impeller chamber of the suction casing for driving the front and rear impellers to rotate, respectively;
• a counter rotating gearset provided outside the impeller chamber of the suction casing for rotating the first drive shaft in a counter direction to a rotating direction of the second drive shaft;
• and
• a forward-reverse rotation shifter provided outside the impeller chamber of the suction casing for shifting the rotating direction of the second drive shaft between a forward direction and reverse direction.