Electric boats work by using an electric motor powered by batteries or other energy storage devices instead of an internal combustion engine (ICE) that runs on gasoline or diesel fuel.
The electric motors on boats are generally direct current (DC) units with relatively simple mechanisms, making them very reliable and easy to operate.
Because an electric motor can reverse direction (unlike an internal combustion engine, which can only rotate in one direction), there is no need for complex gearboxes to move the boat backward.
If the correctly sized electric motor and battery are installed on a boat, and the engine is not held at full throttle, the endurance of the battery will not be a limiting feature,
Apart from the higher upfront costs, electric motors will generally outperform gas-powered motors in almost every metric. Explore the different types of electric boats available in the market and learn about the costs of eco-friendly boats and what factors influence their price.
Now, let’s get into it!
⚡️ How Do Electric Boats Generate Power?
Electric boats are given that name because an electric motor powers them. The electric system will consist of one or a combination of the following components:
- Electric Motor
- Battery Packs
- Charge controller
- Solar panels
- Wind turbine
- Battery charger (Mains)
Solar Electricity Generation
Electric motors are generally rated in amps and volts, while renewable electricity generation devices (solar panels and wind generators) are rated in watts.
To calculate the required specs of solar panels or wind generators, we need to work out the wattage requirements of a motor.
Watts are calculated by multiplying the voltage by the amps. The electrical current, voltage, and watts required by Elco electric motors are listed in the table below.
|Watts consumed per hour
The watts shown in the fourth column determine the solar required panel capacity.
Solar panels rarely produce the power indicated in the specifications. Understand the benefits and options of solar panels for boats and their role in powering electric boats.
Actual Watts Generated
The actual wattage generated is lower than the label indicates. Solar panels are rated based on optimum conditions as follows:
- The solar panel is located at the equator.
- 1000 W/m2 (1 kW/m2) are generated for one hour at noon.
- At a standard ambient temperature of 25oC (77oF).
- A sea level air mass (AM) of 1.5 (1 sun).
The reality is generally different; therefore, the power generated is lower than specified. Learn how to determine the amount of solar power needed for your boat
The Weather Conditions
The weather conditions are a variable factor. As soon as there is cloud cover, the electrical current generated will be reduced.
The Time Of Day
Solar panels are rated during “peak solar hours,” which is a time window during each day when the maximum sunlight is available.
Peak sun hours vary according to the latitude the panels are located in. The different seasons also impact peak sun hours.
Batteries And Charge Controllers
As can be seen, the generation capability of the panels and wind generators is inconsistent.
This means that the energy generated must be stored when maximum solar power is unavailable.
Batteries are used for this purpose. An optimal system will include the following components:
- Electric Motor
- Battery Packs
- Charge controller
- Solar panels (and/or) Wind turbine
The charge controller connects the panels to the battery and ensures the correct current is used for recharging.
The (DC) electric motor is connected to the battery. Under ideal conditions, the solar panels should produce more power than the motor needs to ensure that the excess can be used to recharge the battery(ies). This article covers battery options for electric outboard motors.
A generator could be used to charge the battery if the boat is equipped with an ancillary gas-powered engine. This defeats the point of an electric motor.
Battery Recharger (Mains)
The boat should have access to a battery charger, which can be connected to shore power to recharge the battery.
🛥 How Do Electric Motors Work In Boats?
Marine electric motors use the same principles as any other electric motor. Discover more about electric outboard motors with this comprehensive guide.
How Does An Electric Motor Work?
The motor has a rod (rotor) through the center with copper wires (armature) tightly wound on the rotor shaft. The spinning rotor and armature provide the rotational energy to power the device the motor runs.
The motor casing has two magnets installed on the casing that covers the armature. A series of laminated steel plates cover the armature.
The commutator is a static component installed at the head of the coil in line with the armature. The commutator does not move (remains fixed in place) with the rotor.
The ends of the copper armature’s wires continually touch the commutator.
Each side of the commuter is connected to a DC electric current (negative and positive poles on opposite sides.)
As the armature turns, these wires turn each commutator wire alternates between positive and negative connections.
As the current flows into the commutator from the negative to the positive poles, it moves through the wires on the armature and becomes an electromagnet that generates a magnetic field.
The electromagnet attempts to align itself with the two fixed magnets installed in the casing. When the poles of each magnet line up (positive to positive and negative to negative), they force the armature to spin to around 180o.
At this point, the spin would stop; however, every time the armature rotates 180o, the current reverses, which switches the electromagnet’s polarity around.
The poles are now switched 180o, so they once again repel the magnets, and the motor continues to turn. The process continues, and so the motor spins without interruption.
Although an electric motor generates heat, it is not as great as a gas-powered boat engine which uses heat (explosion) as the primary energy generation.
How Does The Electric Motor Turn The Propellor?
There are two possible ways that an electric motor turns the propeller.
The Motor Is Located On Top
The motor is located in the conventional position at the top of the shaft.
In this instance, the electric motor’s rotor drives a crankshaft, which turns the main driveshaft that runs down the long spine of the motor.
A small gearbox is located at the bottom of the driveshaft. This converts the vertical spinning energy and makes the horizontal prop-shaft rotate. The prop shaft rotates the propellor, which generates thrust and moves the boat.
One of the benefits of an electric motor is that the polarities can be reversed, and the direction of the propellor can be similarly reversed.
The Motor Is Located On The Lower Unit
When the motor is connected directly to the prop shaft and, therefore, the propellor. This is the simplest mechanism and removes the need for the following components:
- Main Drive Shaft
🎭 Advantages And Disadvantages Of Electric Boats
The advantages of using an electric motor to power the boat are as follows:
Performance Benefits (More Torque)
One of the features of an electric motor is that full power is available almost immediately. This can be demonstrated when an electric car has a drag race with an internal combustion engine.
The electric vehicle pulls away immediately and reaches top speed very quickly. If the stretch of road is long enough, the gas-powered car will catch up to the electric vehicle with its higher top speed.
In boating, apart from speed trials and other competitive events, faster “out of the hole” acceleration is more important than top speed.
As electric motors begin to challenge gas-powered units in the power ratings, an example being the Vision Marine’s V32, which produces 180hp, the acceleration power will become a big selling feature.
The price of gas is not only a function of the cost of production but also affected by several other features, including:
- Global politics (it is used as a weapon to punish rogue states).
- The oil-producing nations control the price by varying production rates. When OPEC increases the production rate, the cost goes down, and visa-versa.
- Disasters (such as pandemics, natural disasters, and oil spills).
- Threats of oil supplies running out.
All of this means that boaters who continue to use gas-powered motors are essentially playing the lottery regarding the price they pay.
Electric motors are not subject to these external forces, and once the upfront purchasing costs have been absorbed, the future cost (until the battery needs replacing) is zero.
The maintenance requirements of electric motors are virtually nil due to there being no crankshaft, main drive shaft, or gears. Learn about the lifespan of electric boat motors and what factors affect their longevity.
An electric motor runs almost silently, and the unit creates no exhaust gasses.
Of course, for many boaters, the smell of an internal combustion engine exhaust (particularly an older 2-stroke model) is very emotive. Some may feel that eliminating the sounds and smells reduces the enjoyment of the sport.
To each his own!
Although the production of the batteries (and their end-of-life disposal) presents many ecological challenges, while an electric motor is running, it is a zero-emission device.
This means electric motors do not consume carbon-based, non-renewable energy and do not release harmful emissions, including:
- Carbon monoxide
- Volatile organic compounds
- Nitrogen oxides
- Sulfur dioxide
The disadvantages of using an electric motor are listed below.
Higher Upfront Cost
The cost of purchasing a powerful electric motor and battery system is more than an equivalent gas-powered unit. This is demonstrated in the following table.
|HP (or equivalent kW rating)
|EP-5 Electric Outboard
|5MH Four Stroke
|EP-9.9 Electric Outboard
|9.9E EFI Four Stroke
|EP-14 Electric Outboard
|15MRC Four Stroke
|EP-20 Electric Outboard
|20MRC Four Stroke
|EP-30 Electric Outboard
|30MHGA Four Stroke
|EP-50 Electric Outboard
|50ELPT Four Stroke
|Torque Master 1.75 L RH Camber
The uncharged range of an electric motor is determined by the sized battery used to provide power.
The range of a gas-powered engine is determined by the amount of gas held by the gas tank compared to the engine’s gas consumption.
e-Propulsion has published the table below, showing the range of their 9.9 hp electric outboard at varying throttle settings.
|Range in nautical miles
|4 ½ hours
|2 ¼ hours
|1hour 50 mins
|1 ½ hours
Table sourced from e-Propulsion.
Longer Time To Recharge
Without an onboard solar electric or wind recharging system, a battery used for an electric boat will be completely recharged in hours, not minutes.
If the charge is depleted during the day, it may not be possible to recharge it to continue boating on the same day.
In contrast, the gas tank of a gas-powered boat can be refueled on the water at a suitable refilling station.
🔑 Key Takeaways
1️⃣ Electric motors are a relatively simple technology, making them easy to maintain.
2️⃣Powering them directly from a solar panel is very difficult, and batteries are required.
3️⃣ There are many benefits associated with using an electric motor.
4️⃣ The upfront costs are higher, but savings will be achieved in the longer term.
Although electric motors are not without their problems, they are a reality that will ultimately replace gas-powered units.
Battery technology will advance, the available engine power will increase, and costs will reduce, making them an economic proposition.
Add this to the benefits of using a motor powered by a renewable energy source, the better acceleration, and long-term cost savings, and it becomes a more natural position to adopt.
Anyone looking at a new outboard boat motor with an equivalently sized model available with electric power should consider the options carefully. Compare ePropulsion and Torqeedo electric outboard motors to find the best option for your boat