“It’s our jam” says developer of high torque electric boat motor

June 9, 2025 Jeff Butler 0 Comments Torkmar

UK company Törkmar has launched an easily installed high torque electric boat motor that enables large propeller efficiency for displacement boats travelling on inland waterways.

The company’s motto, ‘Torque is our jam’, reflects the very thorough explanation of torque on their website, noting it is the same twisting force required to unscrew the lid of a jam jar. Less colourfully, it’s the force that your boat’s motor uses to twist the propeller through the water, allowing your boat to move, accelerate, and carry loads.

Why is torque so important for electric displacement boats? A large propeller is more efficient for moving large amounts of water (and the vessel it is attached to) and higher torque turns large propellers more efficiently.

High torque electric boat motor extremely efficient

That large propeller won’t get your boat up on plane, but for narrowboats, canal boats, converted barges and any displacement boat that you want to move slowly and quietly, a large prop at low revolutions per minute delivers gentle, consistent thrust using remarkably little energy. That reduces consumption and extends range.

It’s the same principle applied in large ocean going cargo ships that use huge propellers rotating as slowly as 60-120 RPMs and reaching speeds of 20 knots and a propulsive efficiency of over 95%.

The Törkmar unit is a PMAC (Permanent Magnet Alternating Current) motor wound specially for low speed applications, below 1000 RPM. It was developed by Tim Knox of Mothership Marine, who has designed and built dozens of electric narrowboats along with electric refits of other displacement boats. The motor is the refinement of all that he has learned both from his own experience and the feedback of customers.

Read: Mothership Marine’s solar electric narrowboat

Torque is measured in Newton meters (Nm) or Pound feet (lb-ft). One Newton-meter represents the twisting force of one Newton applied perpendicularly to an arm that is one meter long. A lb-ft is the twisting force of one pound applied to an arm that is one foot long. A lb-ft is about 3/4 of a Nm.

Highest torque rating of motor in its category

The Törkmar has the highest torque rating of any motor in its category: Instant Torque of 245 Nm (180 lb-ft)and Rated (Continuous) Torque of 143 Nm (105 lb-ft) over 60 minutes. It uses only a small percentage of its available 15 kWs of power to turn a 20 inch propeller. That means increased range, extremely quiet operation, and a motor that needs minimal cooling.

“Too much time is spent thinking about the motor and not enough thinking about the propeller,” says Tim. “It’s the propeller that makes the boat move, not the motor.” He calls his way of approaching things ‘back to front thinking’ and says the effectiveness of Törkmar’s propulsion solution can be witnessed simply by observing how the sizing of a kayak paddle matters.

A large paddle is tougher to move through the water simply because of the weight of the water being pushed. A paddle half the width is easier to move, but it has to be paddled twice as quickly to move the same amount of water.

Propellers are like paddles

It won’t get the kayak to reach the same speed as efficiently though. That’s because the water outside the width of the paddle is not moving at the same speed as the water behind it. That difference in speed creates friction, drag at the sides of the paddle, and swirling eddies of water.

Force applied gently over a large area is more effective on water than a harshly applied force in a small area. “Propellers are like paddles,” says Tim. “when water is thrust out of the back of a propeller the faster moving water is subject to friction or drag from the adjacent stationary water. The faster the water leaves the propeller, the greater the drag.”

The differences are even greater with a circular propeller than with a straight edged paddle, because when you analyze a 13″ and 20” propeller, the smaller one doesn’t have 13/20 the surface area of the larger one (65%)…but actually only 43%.

Knox has extended the efficiency of the motor to the efficiency and simplicity of its installation. Whether the work is being done by experienced boat builders or do-it-yourselfers, each step of the instructions is clearly and graphically detailed in the ‘Installation’ section of the Törkmar website.

He has also simplified the throttle installation and systems monitor with a graphic interface that highlights the most important information: Range, RPMs, kW being used, battery state of charge and motor temperature.

For those who may not want to know everything about the intricacies of an electric boat motor, it appears from the Törkmar website that there are already a number of people who think torque is their jam.

“This motor is supremely quiet, powerful and very efficient. We go everywhere at 800W and it is bliss!” say Polly and Tom, owners of ‘Falcon‘ “My boat is called Tranquility,” says Caroline “and she is the very definition: a peaceful, calm state, without noise, violence or worry.” Slapdash Steve sums it up with “I can actually feel my boat accelerate. It’s exhilarating because it’s so quiet! Very happy.”