When it comes to maintaining peak performance in your Mercury 2.5-liter high-performance 2-stroke V6 outboard engine, using premium-quality replacement components is essential. Among the most critical parts to ensure power and reliability are the 1.5mm steel sleeve piston rings, especially for engines using side-pinned pistons.
That’s why Buckshot Racing #77 now offers industry-leading 1.5mm replacement piston rings manufactured by Nippon Piston Ring (NPR) and Riken Rings (RIK)—two of the most respected names in global piston ring production.
These high-performance piston rings are available in two configurations to meet a variety of engine rebuild needs: a Standard Bore 1.5mm ring (NPR), and a Plus .015" Over Bore 1.5mm ring (RIK). Both sizes are engineered specifically for Mercury V6 outboards equipped with steel sleeve cylinders and are direct replacements for Mercury OEM part numbers 39-840684A12 and 39-841139A12 respectively.
Whether you're searching for "Mercury 39-840684A12 piston ring" or "replacement for Mercury 39-841139-A12 overbore ring", these NPR and RIK components ensure perfect fit and performance.
Designed with durability and engine longevity in mind, the NPR and RIK piston rings are produced using high-strength alloy steel, which offers exceptional wear resistance and thermal stability under the extreme conditions of high-RPM outboard engines. Each ring undergoes precision CNC machining and grinding to achieve exact tolerances for thickness, roundness, and ring tension.
Furthermore, surface treatments like phosphate coating and nitriding are applied to reduce friction, enhance lubricity, and improve the ring’s ability to resist wear over long-term use. These premium features ensure that every 1.5mm piston ring for Mercury 2.5L steel sleeve engines performs flawlessly even in the most demanding marine environments.
What sets NPR and RIK apart is their unmatched commitment to quality. Both manufacturers hold internationally recognized certifications, including ISO 9001, IATF 16949, and ISO 14001, confirming their reputation for delivering products that meet the strictest industry standards.
For decades, NPR and RIK have supplied OEM piston rings to top-tier automotive and marine manufacturers worldwide. Their deep legacy of precision engineering and technological innovation makes them the top choice among professional marine mechanics, racers, and performance boat enthusiasts.
These 1.5mm steel sleeve piston rings are specifically compatible with Mercury Pro Max engines such as the 225, 225x, and 260 ROS, as well as Buckshot Racing #77 Super Sport Pistons. Designed for side-pinned pistons, these rings offer unmatched versatility for those rebuilding or upgrading their Mercury outboards.
Whether you’re working with original Mercury Pro Max thin-ringed pistons or installing Buckshot’s high-performance variants, these rings ensure a seamless fit and consistent combustion sealing.
In terms of performance benefits, NPR and RIK rings deliver superior sealing to minimize blow-by and maximize compression, enhanced durability to withstand the punishing combustion pressure of 2-stroke racing engines, and reduced friction for longer piston and cylinder life.
The 1.5mm ring profile ensures optimal contact with cylinder walls, making it the best choice for those looking to maintain or boost engine output without compromising reliability.
For discerning boaters and performance enthusiasts, Buckshot Racing #77 now offers these replacement piston rings at a highly competitive price.
A set of two (2) Standard Bore 1.5mm piston rings is available for just $49, a great value when compared to the Mercury OEM MSRP of $80.54 for part numbers 39-840684A12 and 39-841139A12.
This makes Buckshot’s offering not only technically superior, but also a cost-effective solution for engine builders and racers alike.
If own a Mercury 2.5L high-performance V6 outboard with a steel sleeve cylinder, upgrading or replacing your rings with NPR or RIK 1.5mm replacement piston rings from Buckshot Racing #77 is the smartest choice for performance, durability, and peace of mind.
These rings are precision-engineered, thoroughly tested, and backed by decades of manufacturing excellence—ensuring your engine continues to run at its absolute best, whether you’re on the water for sport, speed, or competition.
Contact mike@buckshotracing77.com or +1-714-697-1716 with any questions.