ISO 8665-2:2024

Overview

ISO 8665-2:2024 specifies requirements for determining and declaring the power of electric marine propulsion systems for recreational and other small craft up to 24 m hull length. The standard defines how manufacturers and test laboratories should measure and report declared (rated) power, whether expressed as motor power or propeller shaft power, and establishes consistent test conditions and reporting practices to support conformity assessment.

Key Topics

• Declaration rules: A declared power value must be accompanied by the declared motor speed and a clear indication of whether the value is motor power or propeller shaft power. Propeller shaft power can be measured directly or disclosed as motor power minus transmission losses.

• Test methods and conditions: The standard outlines representative test sample requirements and environmental reference conditions, including:

  • air temperature: 25 °C ± 5 °C
  • relative humidity: 30 %
  • coolant temperature for liquid-cooled systems: 25 °C ± 5 °C
  • supply from a DC voltage source with maximum voltage drop of 5 % (excluding short periods < 10 s)
  • thermal equilibrium before final readings (temperature rise gradient ≤ 2 K/h)
  • motor speed stability during readings within ±1 % or ±10 min−1, whichever is greater

• Production conformity: In production conformity testing, the measured power at the declared speed shall not deviate from the declared propeller shaft power by more than ±5 % or ±0,45 kW, whichever is greater.

• Test report content: Required report items include motor speed, voltage and current near the motor, net torque at rated output, torque curve, instantaneous initial performance, ambient conditions (temperature, barometric pressure, humidity), coolant temperatures for externally cooled systems, identification of the tested sample, deviations from procedure and the International Standard reference (ISO 8665-2:2024).

Applications

• Supporting manufacturers in publishing accurate and consistent rated power for electric propulsion systems.
• Enabling test laboratories and regulatory bodies to verify declared power and perform production conformity checks.
• Assisting boatbuilders, naval architects and purchasers in comparing and selecting propulsion units based on standardized power declarations.

Related Standards

• IEC 60034-1: Rotating electrical machines - Part 1: Rating and performance (referenced for motor power measurement practices).
• Other parts of the ISO 8665 series for power measurements on small craft.

Practical value: Compliance with ISO 8665-2:2024 reduces ambiguity in power declarations, improves comparability across electric marine propulsion products, and provides a clear framework for testing, reporting and production conformity.