US Patent 7481688 Propulsion unit and boat

A boat can have a propulsion unit connected to a rear surface of a transom plate of a hull. The propulsion unit can have a propeller for producing thrust, a power device for driving the propeller, and a power transmission mechanism for transmitting power from the power device to the propeller. The propulsion unit can also include a braking device configured to exert a generally vertical upward force on the propulsion unit during a braking operation.