Pioneering Sustainable Marine Propulsion

Introduction

On July 28, 2025, YANMAR Marine International introduced a groundbreaking Selective Catalytic Reduction (SCR) system tailored for its 6LY Series engines, marking a significant step toward cleaner and more sustainable boating. This innovative system reduces nitrogen oxide (NOx) emissions by 60-90%, ensuring compliance with the International Maritime Organization’s (IMO) Tier III standards and other global emissions regulations. Designed for both commercial and leisure vessels, particularly those over 24 meters, the SCR system combines cutting-edge technology with a compact, lightweight design, making it a versatile solution for new builds and retrofits alike.

 

Technical Specifications

The SCR system integrates seamlessly with the 6LY Series’ advanced Denso common rail fuel injection system, known for its fuel efficiency and low noise levels. Sensors monitor exhaust temperature and NOx levels, while the ECU calculates the precise amount of Diesel Exhaust Fluid (DEF) to inject. This process converts NOx into harmless nitrogen (N2) and water vapor (H2O), significantly reducing environmental impact.

Design and Functionality

YANMAR’s SCR system stands out for its compact and lightweight design, weighing only 86kg—considerably less than many competing systems. This makes it ideal for retrofitting existing vessels without compromising weight distribution or performance. The system’s integrated bypass and catalytic reactor ensure high-performance NOx reduction while maintaining engine efficiency. For colder regions, such as the Nordics and Baltics, an optional heater kit prevents DEF crystallization at temperatures below -13°C, ensuring reliable operation in harsh conditions.

The system’s compatibility with the 6LY Series, which features a 24-valve cylinder head and re-engineered fuel systems, enhances its appeal. The 6LY engines are celebrated for their high torque, responsive performance, and compact footprint, making them a popular choice for powerboat racing and recreational boating. The addition of the SCR system further elevates their environmental credentials without sacrificing power.

Market Relevance

The global boat market is increasingly focused on sustainability, driven by regulations like IMO Tier III, which mandates an 80% NOx reduction compared to Tier I standards in Emission Control Areas (ECAs). According to industry reports, the recreational boat market is projected to grow significantly by 2033, with a rising demand for eco-friendly propulsion systems (Market Data Forecast). YANMAR’s SCR system positions the company as a leader in this shift, catering to both commercial operators and environmentally conscious leisure boaters.

Compared to other marine SCR systems, such as those from Caterpillar, MAN, and Wärtsilä, YANMAR’s offering is notably compact and easier to install. For example, Caterpillar’s SCR systems emphasize fuel efficiency but may require more space, while MAN’s systems focus on low urea consumption (Pon Power). YANMAR’s system balances size, weight, and performance, making it particularly suitable for vessels with tight engine rooms.

Applications and Versatility

The SCR system is designed for commercial and light-duty commercial vessels operating in ECAs, but its applicability extends to leisure yachts over 24 meters. A notable example is a J Class sailing yacht recently fitted with the system, showcasing its versatility across vessel types (Marine Insight). However, the system is not certified for U.S. navigable waters, limiting its use for U.S.-flagged vessels.

The system’s retrofit capability is a key advantage, allowing older vessels to meet modern emissions standards without requiring extensive modifications. This aligns with the growing trend of retrofitting to comply with regulations like IMO Tier III, which has been in effect since January 1, 2016, for vessels operating in ECAs (YANMAR Technical Review).

Sustainability and Industry Impact

YANMAR’s SCR system is part of its broader Green Challenge initiative, which aims to reduce global emissions through innovative marine technologies. Bas Eerden, Global Sales Manager at YANMAR Marine International, stated, “What we have created with this SCR system is an easier and simpler way to significantly reduce NOx emissions. The system’s uses go beyond adhering to regulations and utilizes the latest technology to make a very significant reduction in emissions” (Hellenic Shipping News).

The marine industry is under increasing pressure to reduce emissions, with the IMO targeting a 50% reduction in greenhouse gas emissions by 2050 (Market Data Forecast). YANMAR’s SCR system not only addresses NOx emissions but also supports the industry’s shift toward cleaner propulsion systems, including electric and hybrid models, which are expected to gain market share by 2030.

Considerations for Boaters

While the SCR system offers significant environmental benefits, boaters should consider the ongoing costs of DEF refills and maintenance. The system requires regular checks to ensure optimal performance, as outlined in YANMAR’s maintenance schedules (YANMAR Marine International). The compact design minimizes installation costs, but operators in colder climates may need the optional heater kit, adding to the initial investment.

Conclusion

YANMAR’s new SCR system for the 6LY Series engines represents a significant advancement in marine propulsion technology. By reducing NOx emissions by up to 90%, it ensures compliance with global regulations while offering a compact, retrofit-friendly solution for a wide range of vessels. As the boating industry moves toward sustainability, YANMAR’s innovation positions it as a leader in eco-friendly marine solutions, appealing to both commercial operators and leisure boaters seeking to reduce their environmental footprint.

For more information, visit YANMAR Marine International or contact a local YANMAR dealer.