Restore factory compression and race-proven reliability with genuine OEM Mercury Gold Piston Rings for Mercury Racing 2.5 Liter V6 two-stroke engines.
 
Designed specifically for Nikasil-plated cylinders, these standard-size (STD) piston rings are trusted by professional engine builders, racers, and performance enthusiasts rebuilding Mercury Racing 260 EFI, 280 ROS, 300 Drag, S3000, and other high-performance 2.5L powerheads.
 
Manufactured by Mercury Marine, these premium gold piston rings deliver the precise fit, sealing performance, and durability required for high-RPM racing engines where compression, ring seal, and heat transfer are critical to maximum horsepower and engine longevity.
 
OEM Mercury Racing
 
This is a genuine Mercury Racing standard-size piston ring set for 3.500-inch bore Mercury Racing 2.5L V6 engines equipped with Nikasil-plated sleeves and top-pin pistons. Cross-reference part numbers include Mercury 817038, 817038A1, 817038A12, 8170381, 840663A12, and 848201A12. Manufacturer part number 39-840663A12.
 
Built for High-Performance Mercury Racing Engines
 
Mercury Racing engines operate under extreme cylinder pressures and sustained high RPM, making piston ring quality one of the most important components during a rebuild.
 
These OEM gold rings provide exceptional compression sealing, efficient heat transfer from the piston to the cylinder wall, and precise oil control to reduce blow-by while maintaining consistent performance throughout the RPM range.
 
Whether you're assembling a championship-winning drag motor, rebuilding a lake racer, or freshening a competition powerhead, genuine Mercury Racing rings help maintain the performance and reliability these engines are known for.
 
Engine Compatibility
 
Designed for Mercury Racing 2.5 Liter V6 engines with 3.500-inch Nikasil-plated cylinders, these rings fit Mercury Racing 260 EFI, 280 ROS, 300 Drag, S3000, Formula 1, Champ, Mod-U, offshore racing, and many custom-built Mercury 2.5L performance engines utilizing standard-bore top-pin pistons.
 
Professional Installation Recommendations
 
Proper cylinder inspection and preparation are essential for maximum ring seal and service life. Cylinders should be thoroughly cleaned and lightly deglazed as appropriate for Nikasil bores before installation.
 
Always verify piston-to-wall clearance, piston groove condition, ring end gap, and cylinder finish before final assembly.
 
Following Mercury Racing factory assembly procedures helps ensure proper ring seating, maximum compression, and long engine life.
 
What's Included
 
Each package includes one (1) pair of OEM Mercury Gold Piston Ring Set containing two (2) piston rings for one (1) piston.
 
A complete Mercury Racing 2.5L V6 engine rebuild requires six (6) ring sets to service all six cylinders.
 
Trusted by Mercury Engine Builders
 
For decades, Mercury Racing engine builders have relied on genuine OEM Gold Rings because of their consistent quality, precise fitment, and proven durability.
 
Whether you're rebuilding a 260 EFI, freshening a 280 ROS, assembling a 300 Drag, or restoring a rare S3000 powerhead, genuine Mercury piston rings remain the benchmark for factory performance and reliability.
 
Contact Mike Hill at +1-714-697-1716 or email mike@buckshotracing77.com for technical support.