Electric vs Gas Outboard Motors

The very first thing to know when looking at electric vs gas outboard motors is to think in terms of kilowatts rather than horsepower.

And this holds across all electrification in the boating industry. Once you grasp this conversion, you’ll be able to look at performance in terms of apples to apples.

The cost analysis too is slightly different and you need to consider the long-term maintenance costs to get a true gauge of which suits your boating needs.

Performance Comparison

The official conversion rate to calculate watts from horsepower is 0.7457 kilowatts per horsepower.

The equivalent kilowatt ratings of engines rated on horsepower are listed below.

To provide a simple comparison, I have prepared a table showing the performance characteristics of three ranges of electric outboard motors compared to the equivalent gasoline-powered models.

๐Ÿ“ Authors Note: All the data has been extracted from the Torqeedo and Mercury websites. Some of the parameters are not disclosed by the manufacturers.

Performance ParameterLow CostMid-RangeHigh End
Torqeedo Cruise 3.0 (Tiller)Mercury 6 hp TillerTorqeedo Deep Blue 25R ElectricMercury 40 HP GasolineTorqeedo Deep Blue 50 ElectricMercury 80 HP Gasoline
Power Output4.5kW (6.0 HP)6Hp (4.5kW)30 kW (40Hp)40 HP (30kW)60kW (80 Hp)80Hp (60kW)
Propulsion TypeElectricGasElectricGasElectricGas
Weight (approx.)19.7 kg26 kg139 kg121 kg146 kg171 kg
Battery TypeLithium-ion 24-voltsN/ALithium-ion 24-voltsN/ALithium-ion 24-voltsN/A
Slow Speed (2 kW โ€“ 6kW Throttle)TBATBA5.0 knots (9.3 km/h)TBA5.0 knots (9.3 km/h)TBA
Top Speed (Full Throttle)TBATBA10 knots (18.5km/h)TBA10 knots (18.5km/h)Varies by boat and conditions
Range 5 knotsTBATBA60 nmVaries by Gas Tank Size60 nmVaries by Gas Tank Size
Range 10 knots16 nm16 nm
Fuel Type24-volts Battery87 octane Gas350 V Battery87 octane Gas350 V Battery87 octane Gas
Noise Level (dB)Almost SilentModerateAlmost SilentModerate to highAlmost SilentModerate to high
EmissionsZero emissionsUltra-Low Emission (3-STAR)Zero emissionsUltra-Low Emission (3-STAR)Zero emissionsUltra-Low Emission (3-STAR)
MaintenanceLow (mainly battery upkeep)Regular MaintenanceLow (mainly battery upkeep)Regular MaintenanceLow (mainly battery upkeep)Regular Maintenance
Cost of Operation1.7kW battery, 2 hours of electricity0.5 gallons per hour40 kW battery 12 hours electrical cost to fully recharge3.8 gallons per hour40 kW battery 12 hours electrical cost to fully recharge10.01 gallons per hour
Acceleration (Equivalent HP)8 HP Instant torque6 HP Gradual Acceleration40 HP Instant torque40 HP Gradual Acceleration80HP Instant torque80HPVaries by model

Electric Outboard vs Gas Cost Analysis

There are several advantages that electric outboard motors have over the equivalent gas-powered models. One of the primary benefits is lower operating costs.

This needs to be balanced out against a slightly higher initial purchase price of the electric outboard units.

Using the outboard motor models listed above, the following compares the initial purchase price, estimated maintenance costs, and the ongoing operating charges.

Purchase Price (excluding Shipping)Low CostMid-RangeHigh End
Torqeedo Cruise 3.0 (Tiller)Mercury 6 hp TillerTorqeedo Deep Blue 25R ElectricMercury 40 HP GasolineTorqeedo Deep Blue 50 ElectricMercury 80 HP Gasoline
Motor$5,759.00$1,870.00$15,000.00$8,346.00$23 999,00$12,744.00
Battery$4,019.00$0.00$14,000.00$0.00$14,000.00$0.00
Total$9,778.00$1,870.00$29,000.00$8,346.00$37,999.00$12,744.00

Maintenance

Gasoline-powered outboard motors require a higher degree of maintenance over the equivalent lifespan of an electric outboard.

Routine maintenance is required annually or every 100 โ€“ 150 hours, whichever comes first.

Normal maintenance would require the following to be checked or replaced:

  • Fuel filters
  • Spark Plugs
  • Oil change (4 stroke models)
  • Oil filters
  • Greasing moving parts
  • Check the sacrificial anode is still useable
  • Check the propellor condition
  • Check the condition of the skeg

The cost of this would be approximately $200.00 (including labor)

In addition to these items, every 300 hours, it is wise to replace the water pump impeller. With labor, this will cost an additional +-$200, depending on where you are located.

Outboard motors are sometimes damaged in unforeseen accidents.

Gas-powered outboard motors are more susceptible to damage in the lower unit.

In my experience, the most common repairs required on an outboard motor are straightening a bent or worn skeg and straightening or replacing the propellor. In extreme cases, work may also be needed on the boat’s propellor shaft and gear system.

Skeg repairs can cost as much as $300 or more, and propeller damage can cost as much as $500 if you need to buy a new one.ย 

If an Insured Event Caused the damage (this will depend on which insurance company you are with), you may only have to pay a deductible.

Assuming that the engine runs for 150 hours per year, the following costs will be incurred every 24 months.

  • Normal maintenance – $400 ($200 times 2)
  • Impeller – $200
  • Cost $600 (every 24 months)
  • Cost $600 (every 24 months)

Cost per year $300

Electric outboard motors have minimal maintenance requirements. Essentially, all you have to do is check the propellor for damage and check the sacrificial anode is still intact.

It is doubtful that any of these items will need replacing for the first couple of years of operation.

I have never had to pay any maintenance costs in the first few years of electric outboard ownership.

Operational Costs

The operating costs are essentially the regular running costs (excluding maintenance and repairs) for every hour of operation.

With electric motors, this is the cost of electricity needed to recharge the battery. Although the cost of electricity varies across different states, for this exercise, I am using a cost of $0.23 per kW.

Gas prices are extremely volatile and vary state by state. For this exercise, I am using a gas price ofย  $3.85 per gallon (Source: Forbes 23 September 2023).

The following assumptions have been made:

  • The motor runs for 6 hours per outing
  • There are 2 outings each weekend
  • The boat is used every weekend for 6 months of the year
The cost of Electricity is $0.23 per kWLow CostMid-RangeHigh End
Torqeedo Cruise 3.0 (Tiller)Mercury 6 hp TillerTorqeedo Deep Blue 25R Electric (40kW * 12 hours)Mercury 40 HP GasolineTorqeedo Deep Blue 50 ElectricMercury 80 HP Gasoline
Cost per session (6 hours)$0.46$11.55$9.20$87.80 $9.20$231.23
Cost per weekend$0.92$23.10$18.40$175.60$18.40$462.46
Cost per year$23.92$600.60$478.40$4,565.60$478,.40$12,023.96

Total Costs over 10 years

Total costsLow CostMid-RangeHigh End
Torqeedo Cruise 3.0 (Tiller)Mercury 6 hp TillerTorqeedo Deep Blue 25R Electric (40kW * 12 hours)Mercury 40 HP GasolineTorqeedo Deep Blue 50 ElectricMercury 80 HP Gasoline
Purchase cost$9,778.00$1,870.00$29,000.00$8,346.00$37,999.00$12,744.00
Maintenance costs over 10 years$0.00$3,000.00$0.00$3,000.00$0.00$3,000.00
Running Costs over 10 years$239.20$6006.00$4784.00$45,656$4784.00$120,230
Total$10,017$10,876$33,784$57,002ย $42,783$135,974

๐ŸŽ“ Editor’s Note: These numbers a based on the assumptions, the lifetime operational costs of each type will vary depending on how often they are used.

Durability and Reliability

Despite the increased cost of ownership of electrical outboard motors, they still make a compelling case in terms of their durability and reliability.

AspectElectric Outboard MotorsGas-Powered Motors
DurabilityTypically have fewer moving parts, reducing wear and tear.Generally have a higher number of moving parts, which may incur more wear and tear.
MaintenanceRequire less frequent maintenance due to fewer parts that can break or wear out.Often require more frequent and extensive maintenance to keep them running.
ReliabilityTend to be more reliable in terms of consistent performance and fewer breakdowns.It can be reliable but may experience issues related to fuel, ignition, and mechanical systems.

Environmental Impact

The clear winners in terms of the environmental impact are electric motors. Although there are some questions regarding the environmental impact of battery manufacturing, the long-term benefits still lean heavily toward electric outboard motors.

Safety Considerations

There are no realistic safety differences between the two power sources. All motors are well-designed. A properly installed electric or gasoline outboard motor is safe, while poorly designed or installed units are not.

I’m the founder and chief editor here at Kite Ship. The electrification of boating is the most exciting thing to happen to the marine industry in a generation! Welcome, and I hope that we can provide the portal you need to dive into the world of electric propulsion and power.