The Beginner's Guide to Electric Outboard Motors

There are many reasons you may be looking into electric outboard motors, they are smooth, quiet, and don’t use smelly gas. In 2021, the performance of the electric outboard is becoming increasingly refined due to competition and the advancements of battery technology in recent years. There is also a growing number of commercial workboats and tugboats that are being used around the world that are 100% electric powered.

Maybe you have a sailboat that needs a new outboard, or you want to fish on one of the increasing numbers of reservoirs, lakes, and bodies of water classified as electric only. So let’s look at the pros and cons of going to a full electric outboard on your boat.

Noise and vibration

Electric-powered outboards provide quieter operation that keeps sailing and fishing more peaceful for you and the fish in the water. Motoring and having a quiet conversation on the water without the rumble and vibration of an internal combustion engine is a big plus. For the sailor, it is more of a seamless experience when motoring, the electric outboard makes it possible to hear the water and wind again.

Some sailors have commented how easy it is to flip a switch on and get out of irons or sticky situations. There is no waiting for glow plugs, or shifting into gear, it’s just ready to go. While this doesn’t make you a better sailor, it is convenient. Low-speed operation of electric outboards can also be handy, there is no clunking in and out of gear; you can go as slow as you want to while docking. Also, most of the larger sail drives and pods offer regeneration under sail power.

Maintenance

The new electric motors have almost nothing to maintain, and no winterizing is needed. Most of the manufacturers build the electric outboards with the motor down in the foot, in line with the propeller. These use passive cooling from the water around them. There are some companies that build their outboards with the electric motor up top, replacing the gas motor, and these will require the standard water pump impeller and gear lube to be replaced occasionally, just like in a gas-powered outboard.

Cutaway of a Torqeedo, showing the brushless motor, planetary gearset and ball bearings on the output shaft

Range and function

The majority of boaters use their boats for a day and come home at night where they can be charged. While initially, the thought is to bring an extra battery along just in case, most users find that the user interface for the majority of electric outboards provides plenty of info to properly plan your day on the water.

Electric outboards, such as the ones from Torqeedo and E-Propulsion, show the state of charge, speed and distance left. With all boats and motors, electric or gas, there is a direct relationship between power usage and speed. Depending on the hull that you have and the way you use the motor can give you a full day on the water at mostly slow speeds, or around an hour and a half at full power.

Batteries and power

Batteries can be charged a discharged rate a certain rate, without damaging them. This is called the C rate, 1C can put out 1 amp for 1 hour. 2C would be able to produce 2 amps but only for 30 minutes. Going the other way, discharging the same battery at 0.5C, or 500mA over 2 hours, will improve the output and life of the battery. Running them at the full potential of what they are able to put out will cause more heat and you will get less power than they are rated for. While lead-acid batteries like to be fully charged every single time, lithium-Ion batteries will live a longer life if only charged to around 80%.

Staying at a high state of charge shortens the life of lithium-ion batteries more than regular cycling does. For this exact reason, the iPhone has the feature to learn your charging habits and when you plug it in at night, it will bring the state of charge to around 80%, and only fully charge it to 100% right before you normally unplug it.

So figuring range, let’s take easy numbers, say you have a 1000watt motor and you run it with a 2000wH battery. In theory, you should be able to run it for two hours at full speed. But in practice when figuring this, you should always add some safety factor, and reserve.

Things like temperature, high and low, can reduce the battery’s output. Running the motor slower, even one or two mph can increase your range exponentially. To learn everything there is to know about batteries, check out Battery University, it’s free, and I highly recommend spending some time reading there, it’s written for the common person to understand.

This graph is an approximation of how much battery you will need to carry. The numbers are based on running at a cruising speed around half power, so if you have a 1000 Watt motor, you would be running around 500W.

The amount of power it takes to push a displacement hull increases exponentially at hull speed, so backing down a few mph can drastically improve your range. But first, you need to decide how much power you want and the battery you will need. And for most people, that’s where the next point comes into play, what can I afford?

Price and Cost

The initial cost for the electric outboards is higher and sometimes significantly higher than the cost of an internal combustion outboard. The electric outboard will cost more, but after a few years, you should break even, with the reduced cost of fuel, spark plugs, oil, and for many of the electric outboards we are looking at, the elimination of the lower unit oil and water pump.

Charging is the next common question, and many of the chargers are 90% efficient, meaning there is a 10% loss in resistance which is turned into heat in the charging process. So if we take that number and charge the biggest battery we have on this list, it is 9 kWh. This battery is the size of some in smaller electric cars. With a 10% loss, we are looking at 9.9 kWh that comes through your electric meter. The average cost per kWh in the US is around $0.12, so multiply that by 9.9 and you get the grand total of $1.18 to charge the battery. So there are significant savings in this area over a gas outboard.

Efficiency

This is where it gets interesting, the available energy in one of the Li-ion batteries supplied for these outboards has 1/100th of the energy density of gasoline. But with the 30% efficiency of a gas motor running in the sweet spot of the powerband and the electric outboard around 60% efficient, so the runtimes for gas and electric outboards up to 5 hp, many times, are not so different. Electric outboards are rated by kW not horsepower, but 1 HP = .75kW, and 1 kW is about 1.3 HP.

So how do you go about choosing an electric outboard?

There is no one right answer for everyone, just like in boats and the car you drive, but you need to find the one that suits your needs, wants, and budget. The motors that come as a complete kit take all the guesswork out of sourcing batteries, making cables, and doing the math. Some of the motors have the batteries mounted right to the motor, and that can be a nice space-saving option in a small boat.

For the motors we are looking at here, portability is also something to consider. Another consideration is, will you have power near your boat to recharge, or will you carry the battery? Some of the smaller motors are very light and come with carrying bags to make it even easier to stow them.

While there are many companies building experimental motors, I only included the ones that are well known. Many others were on my list, but due to old-looking websites, or only showing concepts, to not enough info about them, I weeded it down to these electric outboards. You want to buy from a company that will back their product if you ever have questions or issues.

I also included videos of most of the motors in action.

Torqeedo – Germany

Founded in 2005, Torqeedo combines “torque and speed” in their highly refined electric outboards. They set out to build the best outboard on the market, with their German engineering. These outboards use integrated Lithium-Ion batteries that are integrated on the smaller units and separate on the larger ones. They produce a wide range of power options from the Ultralight 1-3 hp series, up to the Deep Blue 40-80 HP series.

This is their Cruise 2.0 T, Rated for 2 hours at full throttle or 10 Hours at slow speed with their high-performance lithium 3,500 Wh battery.

Input Power in Watts: 2,000W
Max amp draw: N/A
Equivalent Gas Outboard: 5hp propulsive power
Static Thrust in Pounds: 115lb.
Max. Propeller Speed: 1300 rpm
Volts: 24V
Battery: AGM or Lithium-Ion
Long Shaft Length: 29.7 inches
Short Shaft Length: 24.6 inches
Weight: 33.7 lbs SS 35.7 lbs LS Without battery
Motor: Brushless
Cooling: Passive water cooled
Steering Type: Tiller
Throttle: Remote control or Tiller option
Propeller: v19/p4000
Gearing: N/A
Gear oil: N/A
Trim: Manual, or electric
Warranty: Two years limited
MSRP: $3,944 With AGM batteries and charger
MSRP: $5,526 with Lithium-Ion batteries and charger

Torqeedo powers aluminum pontoon boats made by Water Witch in the UK. These boats are trash cleanup boats that are sold around the world, and according to Electrive, the city of Suzhou, in China, has ordered 177 small workboats to clean up its waterways without creating more pollution.

Elco Motor Yachts – New York, USA

Elco was started in New Jersey and made its debut at the World’s Fair of 1893 in Chicago. Fifty-five launches, of varying lengths up to 36 feet long and powered by battery-driven electric motors, carried over a million passengers.

They now build very classic-looking electric outboards that look like a standard gas outboard. The electric motor is located where the gas motor would be and they run off Absorbed Glass Mat (AGM) or Lithium-Ion batteries.

This is their 5hp equivalent, and Elco says that most users get about 4 hours of run time from the standard batteries. That is a mix of use, and not full throttle the whole time. This motor can be bought with 2 AGM batteries that are 12V / 110Ah that weigh 71lbs ea. or 1 Lithium-Ion NCM Battery that is 25.9V / 120Ah that weighs 55lbs.

Their website has an easy-to-use checklist to choose your control style, batteries, and charger that you want to use. They also have an optional electric trim kit for this motor.

Input Power in Watts: 3,000W
Max amp draw: 125 amps DC
Equivalent Gas Outboard: 5hp propulsive power
Static Thrust in Pounds: 95lb.
Max. Propeller Speed: N/A
Volts: 24V
Battery: External AGM or Lithium-Ion
Long Shaft Length: 22.15 inches
Short Shaft Length: 17.15 inches
Weight: 65lb
Motor: Brushless PMAC
Cooling system: Active water cooled
Steering Type: Tiller
Throttle: Remote control or Tiller option
Propeller: 3-7 1/2 x 7
Gearing: 2.08:1 (27/13)
Gear oil: 8.5 Ounces
Trim: Manual, or electric
Warranty: Two years limited
MSRP: $3,944 With AGM batteries and charger
MSRP: $5,526 with Lithium-Ion batteries and charger

Elco has repowered many boats, including a 40-foot tug built in 1928 that works in the canals in New York. Read more about it and other electric tugs and workboats here.

Suzhou Parsun Electric outboards are also powered by Elco motors.

E-Propulsion – Hong Kong

The founder of E-propulsion went to college for robotics and engineering and when the idea stuck to build electric outboards, the fit was perfect. After 6 years of R&D, they released their product to the public. They designed and build 3 – 9.9hp outboards, sail drives with regeneration, and small units for kayaks and standup paddleboards.

One of E-propulsions highlights is their smaller batteries are completely sealed and they float, lessening the worry of accidentally dropping it in the water. The motor system also disassembles without tools and is stored in three matching bags for easy storage and transportation.

This is their Navy 3.0 and it can be used with their 2, 4, or 9 kWh 48V E-Series lithium iron phosphate batteries, depending on your application. The whole motor is rated IP67 waterproof, while not recommended, it can handle being dropped in the water.

This test was done with an 11 foot boat and the E80 4kW battery.

Input Power in Watts: 3,000W
Max amp draw: 63
Equivalent Gas Outboard: 6hp propulsive power
Static Thrust in Pounds: N/A
Max. Propeller Speed: N/A
Volts: 39v -60v
Battery: External lithium iron phosphate
Long Shaft Length: 30.1 inches /76.5 cm
Short Shaft Length: 25.2 inches / 64 cm
Weight: 24.3 kg / 53.6 lbs
Motor: Brushless DC motor
Cooling system: Passive water cooled
Steering Type: Evo Tiller / Evo Top Mount Control / Evo Side Mount Control / Evo Dual Remote Control
Throttle: Remote control or Tiller option
Propeller: 10.2″ × 6.7″ 2-blade composite propeller
Gearing: Direct drive
Gear oil: N/A
Trim: Manual
Warranty: Two years limited
MSRP: $5,022 tiller and E80 batteries and 20 amp charger
MSRP: $6,647 with tiller and E175 batteries and 40 amp charger

Karvin – Czech Republic

Karvin offers electric outboards from 16 – 24 hp, running on 24 to 48 volts. Here we have the Karvin 4500, the 16 hp model.

Input Power in Watts: 4,500W
Max amp draw: N/A
Equivalent Gas Outboard: depends on voltage 8 / 12 / 16
Static Thrust in Pounds: 295 lbs
Max. Propeller Speed: depends on voltage 900 / 1200 / 1500 rpms
Volts: 24V / 36V / 48V
Battery: LiFePO4, LINiMnCoO2 (NMC) or AGM
Long Shaft Length: N/A
Short Shaft Length: 380mm
Weight: 25.5 kg / 56.2 lbs
Motor: Brushless DC motor
Cooling system: Passive water cooled
Steering Type: Tiller
Throttle: Tiller option
Propeller: stainless steel
Gearing: Direct drive
Gear oil: N/A
Trim: Manual
Warranty: N/A
MSRP: $5,164 without battery

Aquamot – Netherlands

With the goal of providing clean power on the water when it wasn’t popular yet, Aquamot successfully was one of the pioneers. Today making outboards, direct drives, and sail drives using their silicon battery technology, they are seeing almost zero downtime on their units. Here we are looking at the Trend 1.8L-P with integral battery.

Input Power in Watts: 1,800W
Voltage: N/A
Max amp draw: N/A
Equivalent Gas Outboard: 5.5 hp
Static Thrust in Pounds: 94 lbs
Max. Propeller Speed: N/A
Battery: Li-Ion Integrated, removable
Long Shaft Length: N/A
Short Shaft Length: 75cm / 29.5 inches
Weight: 14.9 kg / 32.8 lbs
Motor: Brushless DC motor
Cooling system: Passive water-cooled
Steering Type: Tiller
Throttle: Tiller
Propeller: Plastic
Gearing: Direct drive
Gear oil: N/A
Trim: Manual
Warranty: 2 Year
MSRP: $2665 with battery

Aquamot Longlife Silicon Battery that can be used to extend range, or be used with one of the larger motors

Combi – Netherlands

Combi Outboards has a rich history as a pioneer in the Netherlands in the field of electric propulsion since 1979. In 2002 they brought to the market the first brushless permanent magnet motors.

Input Power in Watts: 1,500W Output power S1
Voltage: 24
Max amp draw: N/A
Voltage: 24-48
Max amp draw:
Equivalent Gas Outboard: 5 hp correct
Static Thrust in Pounds: N/A
Max. Propeller Speed: 1350
Battery: AGM, Lithium-Ion or LEAD ACID (Deep Cycle) not included
Extra long shaft length: 57.2 cm
Long Shaft Length: 52.5 cm / 20.5 inches
Short Shaft Length: 40.6cm / 15.9 inches
Weight: 29 kG
Motor: Asynchronous AC motor and IPM motor
Cooling system: Passive water-cooled
Steering Type: Tiller and Remote
Throttle: Tiller or joystick
Propeller: 220mm Aluminum
Gearing: Direct drive
Gear oil: N/A
Trim: Manual and manual tilt
Warranty: 2 Year
MSRP: $4369.00 without battery or export fees.

Combi powers the recycled plastic canal boats in Amsterdam for Plastic Whale, who fish for trash and plastic before it reaches the ocean. Read more about them and their “Old Fashioned Plastic Fishing” and what they do with the plastic here.

Aquawatt – Austria

Aquawatt has been building and designing electric outboards since the early 90s when their design was named fastest electric boat in 1991. Today using Yamaha housings, they are converting the motors to electric. They are building electric outboards with up to 70 hp today. We are looking at their 20 hp equivalent here today.