Jet skis historically used two-stroke engines for propulsion due to their compact size, lightweight, and high power-to-weight ratio, which are advantageous for watercraft. Due to environmental concerns and regulations, there has been a significant shift towards four-stroke engines in recent years.

Here’s an overview of both engine types in jet skis…

Two-Stroke Engines

• Advantages
  • Power-to-Weight Ratio – Two-stroke engines are typically lighter and more powerful than four-stroke engines of similar size, making them ideal for applications where weight and power are critical factors.
  • Simplicity – They have fewer moving parts and do not require a separate lubrication system, simplifying maintenance.
  • Performance – Two-strokes can achieve higher RPMs and, thus, higher speeds, which is desirable for racing and high-performance applications.
• Disadvantages
  • Emissions – Two-stroke engines produce more emissions, including unburned hydrocarbons and particulate matter, than four-stroke engines. This has led to regulatory concerns regarding air and water pollution.
  • Fuel Efficiency – They are generally less fuel-efficient than four-stroke engines.
  • Noise – They tend to be louder than four-stroke engines.

Four-Stroke Engines

• Advantages
  • Lower Emissions – Four-stroke engines produce lower emissions of pollutants like hydrocarbons and carbon monoxide, making them more environmentally friendly.
  • Fuel Efficiency – They are typically more fuel-efficient than two-stroke engines.
  • Quieter Operation – Four-stroke engines operate more quietly than two-strokes, enhancing the boating experience.
• Disadvantages:
  • Complexity: They have more moving parts and require a separate lubrication system, which can increase maintenance complexity.
  • Weight: Four-stroke engines are generally heavier than two-strokes of similar power output, affecting performance in some applications.

Industry Trends

• In response to environmental regulations and consumer demand for cleaner and quieter engines, many manufacturers have shifted towards producing jet skis and personal watercraft with four-stroke engines. These engines offer improved environmental performance without compromising significantly on performance or reliability.
• Some high-performance and racing models may still utilize two-stroke engines due to their power-to-weight advantages and specific performance characteristics.

While jet skis historically used two-stroke engines, there has been a notable transition towards four-stroke engines in recent years due to regulatory pressures and advancements in engine technology. Both types have pros and cons, and the choice often depends on factors such as performance requirements, environmental considerations, and regulatory compliance.