A marine propulsion unit has at least one motor for rotating a pitchable propeller around an axis. The pitchable propeller is connected with a first shaft and a second shaft, the first shaft being rotated by a first power way and the second shaft being rotated by a second power way. The first power way and the second power way are controllable independently of each other so that a first rotation speed (rpm) of the first shaft and a second rotation speed (rpm) of the second shaft can vary in relation to each other. A coupling is arranged between the first shaft, the second shaft and the pitchable propeller for changing a pitch angle of the pitchable propeller when the first rotation speed and/or second rotation speed vary in relation to the other.

A marine propulsion unit has at least one motor for rotating a pitchable propeller around an axis. The pitchable propeller is connected with a first shaft and a second shaft, the first shaft being rotated by a first power way, the second shaft being rotated by a second power way. The first power way and the second power way are controllable independently of each other so that a first rotation speed (rpm) of the first shaft and a second rotation speed (rpm) of the second shaft can vary.

A transmission for a human-powered vehicle. The transmission has a primary system that includes a transmission case, a crankshaft with cog, a pair of receiver cranks, a pair of connecting rods, a pair of oscillating driver cranks, and a pair of pedals. A secondary biasing system is engaged with the primary system to provide a favorable torque around dead centers of the primary system. The transmission 150 may be configured to transmit power by driveshaft, chain, or belt to drive a wheel or propeller. In a watercraft application, an operator alternatingly applies force to a pair of pedals while seated close to the floor of a kayak 145. Power from the transmission is transmitted through a steerable lower gear case 134 via a propeller to propel the craft. The operator maneuvers the craft by means of a control lever 135 operably connected to the lower gear case by cables 136.