Abstract: To reduce engine exhaust gas pressure behind a motorboat propeller formed with a boss for educing engine exhaust gas therethrough, without forming a trumpet-shaped boss end and without allowing exhaust gas to flow upstream along the boss outer surface, a single or plural small subblades are provided between two adjacent large main blades at such a position that a positive pressure domain produced by the subblade reduces a negative pressure domain produced by the main blade. Since engine exhaust gas can be effectively educed, engine power increases and therefore motorboat acceleration performance can be improved.

Abstract: An apparatus for controlling a plurality of driving units comprises a lever device pivotable to operate each driving unit, and a switch device having a plurality of switches each for changing the position of a driving portion of each driving unit. The switch device is disposed in the lever device such that the lever device and thed plurality of switches are simultaneously manually operated.