Thrust to Horsepower: The Power of Electric Boats

The terms thrust, horsepower, kilowatts, and speed are regularly bandied about by mariners trying to rate an electric boat’s performance.

Each of the metrics has very different meanings in the electric boat vocabulary.

Horsepower (hp) and kilowatts (kW) are measurement units used to define how much power an electric motor can produce to propel a boat forwards or in reverse.

To better understand the relationship between these units and how they apply to electric motors, it’s helpful to learn about converting kilowatts to horsepower.

Thrust is a measure or the effect of horsepower and kilowatts. The higher the motor horsepower and the more optimal the shape of the propellor, the greater the thrust that is produced.

🎓 Understanding Thrust And Horsepower

The meanings of the words thrust and horsepower are explained below.

Definitions Of Thrust And Horsepower

Thrust and horsepower are measures of the amount of work performed. The difference is that horsepower expresses the measurement in terms of time, whereas thrust measures the force applied to move an object over a known distance.

The definitions of thrust and horsepower are more fully explained below.

Horsepower

Horsepower is the energy needed to lift an item weighing 75 kilograms (165 pounds) to a height of one meter per second (ft-lbs./s.)

The estimate of an engine’s horsepower can be calculated when the thrust and speed are known and can then be used to multiply.

Horsepower can be calculated using the following formula Horsepower = thrust * Velocity / 375.

Thrust

Thrust is the result of the application of horsepower. It means that thrust is the process of converting that force into motion and is measured against the distance moved (lbs./ft.)

As the throttle is opened and the engine produces more horsepower, the thrust value is increased, and the boat moves over a larger distance.

How They Relate To Electric Boat Motors

Thrust is the result of the electric motor consuming kilowatts and producing horsepower.

If the engine horsepower, the propellor dimensions, and the rotational speed are known, thrust can be calculated.

Selecting an optimally sized motor for a specific boat shape ensures efficient performance and better boat control. For example, understanding the significance of trolling motor thrust is crucial for maintaining boat control and maneuverability in various water conditions.

Factors That Impact Thrust And Horsepower In Electric Boats

The factors that affect the thrust produced on an electric boat motor are as follows:

The horsepower or kilowatt rating of the boat’s engine.
The propellor pitch.
The shape of the blades (mainly aspect ratio and sweep).
The size of the blades (propellor diameter).
The number of blades.
The speed in revolutions per minute.

💡 Note: A boat motor’s horsepower/kilowatt rating is directly affected by the battery’s voltage capacity(s).

The Differences Between Thrust And Horsepower

Thrust and horsepower are work measurements; however, horsepower is measured as a factor of time, while thrust is a measurement as a distance factor.

Because of this, there is no direct mathematical relationship between horsepower and thrust without including the speed of the electric boat.

Thrust can be calculated using the known engine horsepower in the following formula.

Thrust = horsepower x constant value/ Rpm (rotations per minute) x a factor for the propellor inefficiency.

The constant value results from converting the horsepower into a rotational value. This is achieved by dividing the horsepower by 2π.

As discussed earlier, horsepower is calculated by the following formula.

Horsepower equals thrust * Velocity / 375.

🚀 Maximizing Thrust In Electric Boats

Maximizing an electric boat’s thrust enables the boat to accelerate more quickly and achieve a higher top speed.

Tips For Increasing Thrust

The thrust produced by the electric motor is affected by the following scenarios:

Change The Profile Of The Propellor

Without increasing the size of the electric motor, the thrust can be increased by adjusting the following propellor characteristics.

Increasing the size (diameter) of the propellor without changing the pitch generates more thrust.
Changing the pitch of the propellor to a steeper (more acute) value without increasing the propellor diameter increases the thrust.

Therefore, fitting a new differently sized or shaped propellor will change the thrust values.

The propellor pitch can be compared to a motor car’s gears. The more acute the blade’s angle (low gear in a car), the higher the thrust (acceleration). However, just as you can’t go at high speeds in low gear, so the boat’s top speed is reduced.

Create More Horsepower

The thrust will be increased if the horsepower is increased. There are three ways to increase an electric motor’s horsepower:

Add more batteries into the system to increase the voltage.
Change the engine for a higher output model.
Check that the optimal gauge wiring cables are used to ensure the maximum current flow (amps).

Maintenance And Upkeep To Maintain Optimal Performance

There are a few actions that will assist in the long-term performance of the electric boat:

Keep the hull clean.
Ensure that the propellor is in good condition and is not bent, unbalanced, or chipped.
Ensure that the propellor is installed at the correct depth.
Ensure the battery is maintained properly.
Never discharge the battery to a lower level than recommended by the manufacturer.
Keep the weight in the boat to a minimum.

🚤 Real-World Examples Of Electric Boats With High Thrust

Manufacturers can do several things to increase the thrust and speed of electric motors:

Increasing the effective power rating of the electric motor (hp/kW).
Reduce the amount of the hull which contacts the water.
Streamline the shape of the hull.
Lower the boat’s overall weight.

Case Studies Of Electric Boats With Exceptional Thrust And Horsepower

The fastest electric boat is claimed to be the Vision Marine’s V32 which has achieved a top speed of 109 mph.

The Role Of Thrust And Horsepower In The Vision Marine’s V32 Performance.

The boat achieved the record in front of 100,000 spectators on 8th August 2022 at the Lake of the Ozarks.

The biggest factors which enabled the speed are listed below.

The hull was the widebody 32′ catamaran (ensuring the smallest hull contact with the water).
The boat was stripped of all non-essential weight-creating components.
Two high-powered E-Motion™ 180E engines produced 180hp each (thrust is not known).

These three factors worked together to produce the world record.

🔑 Key takeaways

To wrap up, the most critical takeaways from the article are

1️⃣ Thrust is the result of applying horsepower or kilowatts, with higher motor horsepower and more optimal propellor shape leading to greater thrust production.

2️⃣ Horsepower and thrust are both measurements of work, but horsepower is measured in terms of time, while thrust measures the force applied to move an object over a known distance.

3️⃣ Maximizing thrust in electric boats can be achieved by changing the propellor’s profile, creating more horsepower, or increasing the battery size.

If you are wondering what to learn next, I recommend discovering how electric boats function to learn more about their propulsion systems.