How to choose the power of the main engine for your boat?

Dominik Kolka
Knowledge
905 odwiedzin
ePropulsion

Selecting the right electric motor power is one of the most important steps when planning a propulsion system retrofit or building a new vessel. ePropulsion high-voltage motors from the X series (outboard) and I series (stationary) offer a wide power range - from 10 kW to 40 kW - but which one will be right for your boat?

The manufacturer emphasizes that power selection is based on several key design parameters and your performance expectations.

ePropulsion logo – manufacturer of electric outboard and stationary motors

Key Parameters for Power Selection

Proper electric motor power selection requires consideration of several important design and operational factors:

1. Boat Weight

The heavier the vessel, the more power is needed to efficiently get underway and maintain comfortable speed.

Consider:
  • ✓ Dry hull weight
  • ✓ Crew and passengers
  • ✓ Deck equipment
  • ✓ Fuel (hybrid boats)
  • ✓ Water and supplies

2. Waterline Length and Beam

These parameters determine the hydrodynamic resistance of the hull.

Long and narrow

More efficient

Short and wide

Require more power

3. Hull Height

Greater height increases air resistance, especially at higher speeds.

Additional power reserve needed with:
  • ⚠ Massive superstructure
  • ⚠ High freeboard
  • ⚠ Navigation in windy conditions

4. Expected Speed

The most important criterion - you decide on the target speed.

9-13 km/h
X12, I10
15-20 km/h
X20, I20
22-28 km/h
X40, I40

Speeds are given as examples based on a 1000kg boat with 3m length.

Power Selection Calculator - Check with Examples

See how parameters of different boats affect motor power selection. Click on a selected boat to view calculation details:

Whaly 455R (2025)
Whaly 455R

Whaly 455R - compact electric boat (RIB) with X20 motor

Length:
4.50 m
Beam:
1.75 m
Weight:
594 kg
Max speed:
24 km/h
Applied: X20-L (20kW)
Berkshire 20CL LE (2025)
Berkshire 20CL LE

Berkshire 20CL LE - medium pontoon boat with X20-XL motor

Length:
6.35 m
Beam:
2.60 m
Weight:
1000 kg
Max speed:
19.3 km/h
Applied: X20-XL (20kW)
Balt Yacht SunCamper 31
Balt Yacht SunCamper 31

Balt Yacht SunCamper 31 - large boat with X40 motor

Length:
9.45 m
Beam:
3.05 m
Weight:
4130 kg
Max speed:
14.9 km/h
Applied: X40-L (40kW)

What does the selection process look like?

The ePropulsion manufacturer, based on the mentioned parameters (weight, length and width of waterline, draft depth, expected speed), can indicate the recommended motor power - of course as a guide, because each boat design is different.

This means that approximate data is sufficient to determine at the investment planning stage whether, for example, X20 would be a better choice, or whether a more powerful X40 unit will be necessary.

Why X and I series?

High voltage 96V

Minimal losses and maximum energy transmission efficiency.

Power range 10-40 kW

Adapted to different vessels - from small boats to larger yachts.

Integration with eSSA system

Full control of operating parameters and monitoring of all functions.

Hydrogeneration

Possibility of energy recovery while sailing under sails.

Reliability

No fuel, oil, filters and complicated maintenance.

Simplicity

Easy installation and virtually maintenance-free operation.

FAQ – most frequent questions about power selection

Boat weight (with equipment), length and width at waterline, draft depth, hull height and expected maximum speed are needed.

Yes, a higher power motor will give you reserve for the future and better performance, but it will be more expensive and may mean higher energy consumption during normal operation.

X series are outboard motors, I series are stationary (inboard) motors. Both operate at 96V voltage and offer similar power ranges of 10-40 kW.

Approximate determination is possible, but we recommend consultation with the manufacturer, because each boat has different characteristics and each design is different.

A motor with too little power simply won't achieve the expected speed. A motor with too much power will be more expensive, but will provide greater versatility and power reserve for the future.

Summary

Selecting the power of an electric motor for a boat is not random - it requires analysis of the vessel's construction and your speed expectations. Weight, waterline, hull height and target speed allow the manufacturer to indicate the optimal model from the ePropulsion X or I series.

Thanks to this, you gain confidence that your boat will sail efficiently, comfortably and in accordance with the vision of modern, emission-free navigation.

Need help selecting motor power?

Do you have questions about selecting the appropriate power for your boat? Want to consult the technical parameters of your vessel?

Contact us – our experts will help you select the optimal ePropulsion X or I series motor tailored to your boat's construction and performance expectations.

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