A modular hybrid propulsion unit is disclosed that is mountable to a watercraft. According to an example, the modular hybrid propulsion unit includes a housing configured to fit within a complementary housing receiver on a topside of the watercraft, and a rotational output coupling configured to rotationally engage with a rotational input coupling for a propeller of the watercraft. The propulsion unit further includes an electric motor within the housing, the electric motor having a motor shaft connected to the rotational output coupling for providing an electrically powered rotational input to the rotational output coupling. The propulsion unit further includes a crank having one or more crank arms. The crank is connected to the rotational output coupling for providing a human powered rotational input to the rotational output coupling independent of the electrically powered rotational input by the electric motor.