A watercraft battery cooling system 1 comprises: a coolant channel 12 through which coolant circulates to cool a battery 5; a cooling water channel 13 through which cooling water flows; and a heat exchanger 14 for exchanging heat between the coolant and the cooling water. The cooling water channel 13 includes a tank 21. The cooling system is configured such that, when a watercraft equipped with the system is on-water, the water can be stored in the tank 21, and that, when the watercraft is on land during battery charging, the water stored in the tank 21 can be used to circulate through the cooling water channel 13 as cooling water.

A watercraft battery cooling system 1 comprises: a coolant channel 12 through which coolant circulates to cool a battery 5; a cooling water channel 13 through which cooling water flows; and a heat exchanger 14 for exchanging heat between the coolant and the cooling water. The cooling water channel 13 includes a tank 21. The cooling system is configured such that, when a watercraft equipped with the system is on-water, the water can be stored in the tank 21, and that, when the watercraft is on land during battery charging, the water stored in the tank 21 can be used to circulate through the cooling water channel 13 as cooling water.

Disclosed is a re-liquefying device using a boil-off gas as a cooling fluid so as to re-liquefy the boil-off gas generated from a liquefied gas storage tank provided in a ship. A boil-off gas re-liquefying device for a ship comprises: a multi-stage compression unit for compressing boil-off gas generated from a liquefied gas storage tank; a heat exchanger in which the boil-off gas generated from the storage tank and the boil-off gas compressed exchange heat; a vaporizer for heat exchanging the boil-off gas cooled by the heat exchanger and a separate liquefied gas supplied to a fuel demand source of a ship, and thus cooling the boil-off gas; an intermediate cooler for cooling the boil-off gas that has been cooled by the heat exchanger; and an expansion means for branching a part of the boil-off gas, which is supplied to the intermediate cooler, and expanding the same.

A driving unit for an electric tunnel thruster. Such driving unit includes an electric motor, a controller and a support for mounting the electric motor and its controller on a tunnel of the tunnel thruster. The electric motor and the controller have separate housings and are mounted separately from each other to the electric motor support that is also a heat conductive radiator element for cooling the controller, and at least one heat radiating surface of the controller is contacted to at least one heat-absorbing surface of the electric motor support.

A driving unit for an electric tunnel thruster. Such driving unit includes an electric motor, a controller and a support for mounting the electric motor and its controller on a tunnel of the tunnel thruster. The electric motor and the controller have separate housings and are mounted separately from each other to the electric motor support that is also a heat conductive radiator element for cooling the controller, and at least one heat radiating surface of the controller is contacted to at least one heat-absorbing surface of the electric motor support.

A personal watercraft comprises a deck having coupled thereto a hull defining a bottom wall, a rear wall and a water intake extending from the bottom wall to the rear wall, and a jet propulsion system. The jet propulsion system comprises a housing coupled to the rear wall and defining an inlet to receive water from the water intake, a venturi, and an outlet to expel the water, and comprises a rim-driven motor disposed within the housing between the inlet and the venturi. The rim-driven motor defines a center axis and comprises a stator coupled to the housing, a rotor disposed radially inwardly of the stator relative to the center axis, and impeller blades coupled to the rotor and projecting towards the center axis, the rotor and the impeller blades rotatable about the center axis to draw the water via the inlet and expel the water via the outlet.

an Axial Flux Propulsion System for an Electric Boat which includes interconnecting subsystems including a mounting system, a traction system, a transmission system, an electrical power distribution system, a control system, and a fluid management system among other boat systems. The traction system being an axial flux motor/generator.

A liquid container according to the present invention includes: a container 2 temporarily storing a fuel; and a drain unit 3 discharging the fuel from a communication hole 11 provided at a lower portion of the container 2, and the drain unit 3 includes a valve body 15 formed of metal with higher strength and hardness than those of the container 2 made of resin, including a drain passage establishing communication between the communication hole 11 and outside and a valve seat facing the drain passage, which are formed therein, and detachably fixed to the container 2, and a drain screw 16 having a valve element attached to the valve body 15 for opening and closing the drain passage by being separated from or abutting the valve seat.

A liquid container according to the present invention includes: a container 2 temporarily storing a fuel; and a drain unit 3 discharging the fuel from a communication hole 11 provided at a lower portion of the container 2, and the drain unit 3 includes a valve body 15 formed of metal with higher strength and hardness than those of the container 2 made of resin, including a drain passage establishing communication between the communication hole 11 and outside and a valve seat facing the drain passage, which are formed therein, and detachably fixed to the container 2, and a drain screw 16 having a valve element attached to the valve body 15 for opening and closing the drain passage by being separated from or abutting the valve seat.

Aspects of the present disclosure are directed to a method of refueling an electric watercraft. The method may include detecting, by one or more sensors, an unlock signal as a function of unlocking a first battery pack from a first receiver, receiving, by a computing device, the unlock signal, and disabling, by the computing device, the first battery pack and a second battery pack simultaneously, in response to receiving the unlock signal. Disabling the first battery pack and the second battery pack may further include disabling the first battery pack using a first contactor and the second battery pack using a second contactor. Aspects of the present disclosure may also be direct to a system for refueling an electric watercraft.