PURPOSE: To rectify water and to improve propulsion efficiency by arranging at least two sheets of garbage removing plates for removing garbage attached to a grill and by providing these removing plates at the upper part of an intake port so that they hold a drive shaft between them.

CONSTITUTION: A garbage removing plate 34 is operated, for example, so that it is moved downward by an operating tool such as a lever or the like, and by this, it is moved from the upper part of a grill 35 to the grill side so as to remove garbage attached to the grill 35 portion. Also, in the state where it is stored at the upper part, as the garbage removing plate 34 is provided along the flow direction of water flow, it rectifies the water flow, and further in the case where a rope which has intruded from a grill 25 portion is wound around a drive shaft 18, the removing plate 34 arranged so that it holds the drive shaft 18 prevents the rope further wound into the casing side.