The Buckshot Racing #77 Mercury 2.4L WSM Dual-Ring Piston Kit is a complete six-cylinder rebuild package for compatible Mercury and Mariner 2.4-liter V6 two-stroke outboards.
 
These engines powered many classic Mercury performance and recreational models from the late 1970s through the early 1990s, including 150, 175, 200, 220 and 225 HP applications.
 
The kit includes six dual-ring pistons, six slip-fit wrist pins, twelve piston rings and twelve wrist-pin clips. It is available in multiple bore sizes to cover original standard-bore engines as well as blocks rebuilt with oversize steel sleeves.
 
Standard 3.375" Chrome Bore
 
The standard option is for compatible Mercury 2.4L blocks retaining the original-style 3.375-inch chrome-plated cylinder bore. This version should be used only when the cylinder plating remains serviceable, the bore is within specification and the supplied ring package matches the chrome-plated running surface.
 
Chrome-bore and steel-sleeve engines require different ring materials, so ring selection should always be matched to the actual cylinder surface rather than engine model alone.
 
.010" Oversize Steel Sleeve
 
The .010-inch oversize piston is intended for properly machined steel or cast-iron sleeves with a nominal bore of approximately 3.385 inches. This size allows a lightly worn sleeve to be cleaned up without removing more material than necessary.
 
.015" Oversize Steel Sleeve
 
The .015-inch oversize option is designed for a nominal 3.390-inch steel-sleeve bore. This intermediate size is useful when the cylinder requires more cleanup than .010 but does not need to be taken directly to .030 oversize.
 
.030" Oversize Steel Sleeve
 
The .030-inch oversize piston fits a properly finished steel sleeve with a nominal bore of approximately 3.405 inches. This is a common rebuild size for Mercury 2.4L blocks that have experienced wear, scoring or previous cylinder repair.
 
.040" Oversize Steel Sleeve
 
The .040-inch oversize version is intended for a nominal 3.415-inch steel-sleeve bore. Before machining to this size, confirm that the installed sleeve has sufficient wall thickness and remains suitable for the intended horsepower and RPM range.
 
Mercury 2.4L V6 Applications
 
These WSM piston sets fit many Mercury and Mariner 2.4L V6 two-stroke engines in the 150-225 HP range, depending on year and configuration. Common engine families include V-150, V-175, V-200, Black Max, XR4, Magnum II, Laser EFI, XRi, 220 Laser, and various 2.4L EFI and high-performance applications.
 
Because these engines are now decades old, many blocks have been resleeved, replated or rebuilt with parts from different production years. Fitment should therefore be confirmed by actual bore size, cylinder material and piston configuration—not horsepower or engine decals alone.
 
Cylinder Preparation Before Installation
 
Before installing new pistons, every cylinder should be measured for diameter, taper and out-of-round. The bore should be nearly perfectly round and within the piston manufacturer’s required clearance.
 
Steel sleeves should have a fresh crosshatch hone pattern to retain oil and help the rings seat correctly. A polished or glazed cylinder should be properly honed before assembly.
 
Inspect all bores for chips, cracks, scoring, worn spots, damaged port edges or deep vertical grooves. Sharp or damaged port edges can catch a piston ring and quickly destroy a fresh rebuild.
 
Ring end gap should also be checked in the actual cylinder where each ring will run. Final piston-to-wall clearance and ring-gap specifications should follow the instructions for the exact WSM piston and bore combination.
 
Mercury Part Number Cross References
 
This 2.4L piston family is commonly associated with Mercury 8667A22, 8667A42 and 8667T42, along with Sierra 18-4550 for standard-bore applications. Buckshot Racing #77 also references the complete six-piston package under 100-10-77.
Individual Port and Starboard piston numbers may vary by bore size, so verify the exact piston set before ordering.
 
Buckshot Racing #77 Tech Tip
 
The most important step before ordering a Mercury 2.4L piston kit is identifying what is actually inside the block. An engine that originally left Mercury with chrome-plated cylinders may now have one or more steel sleeves from previous repairs.
 
Measure each cylinder, confirm the running surface, then choose the correct standard or oversize piston and ring combination.
 
The Buckshot Racing #77 WSM Mercury 2.4L Dual-Ring Piston Kit provides a complete six-cylinder solution for standard 3.375-inch chrome-bore engines and properly prepared .010, .015, .030 and .040 oversize steel-sleeve applications.
 
Contact Mike Hill with technical questions at +1-714-697-1716