The Vertex Thin (1.5mm) Ring Piston Kits are a premium replacement for Mercury V6 2.5L 2-stroke engines produced for the bottom-guided 1991 motor. This piston is a top choice of Mercury outboard drag racers.
 
These 1991 model year 2.5 pistons can be adapted to the later 1992-2005 Top Guided Rods with the Wrist Pin Conversion Washer!
 
Designed to meet the needs of high-performance marine applications, these kits are compatible with various horsepower models, including 150 HP, XR6, 175 HP, XRi, 200 HP, 225 Pro Max, 245 Carb, 260 EFI, 280 ROS, S3000, and 300 Drag HP outboard engines.
 
Each set includes six (6) complete piston kits, providing all necessary components—piston, 1.5 rings, wrist pin, and circlips—for a straightforward and precise installation.
 
Two-stroke engines operate under different conditions compared to four-stroke engines, with lower cylinder pressures and a greater emphasis on thermal efficiency.
 
Cast pistons, like those in the Italian Vertex kits, excel in these environments due to their unique material properties. Vertex pistons are gravity-cast from a high-silicon aluminum alloy containing 18% silicon, making them highly suited for two-stroke applications.
 
Reduced Thermal Expansion: The high silicon content minimizes thermal expansion, allowing these pistons to maintain consistent geometry at operating temperatures. This enables tighter tolerances, which result in better power output, improved performance, and reduced risk of piston slap or rattling.
 
Enhanced Durability: Silicon improves wear resistance, extending piston life by reducing skirt wear. This characteristic is especially important for engines subjected to high RPMs and continuous operation, as seen in marine environments.
 
Vertex pistons are designed to deliver OEM-level fitment and performance while exceeding durability standards. With a 3.500-inch bore and advanced machining techniques, these pistons ensure compatibility with the Mercury V6 2.5L engine platform. Key features include:
 
Anti-Friction Coating: The piston skirts are coated to reduce friction, improve lubrication, and enhance longevity.
 
Complete Kit: Each kit includes a piston, rings, wrist pin, and circlips, providing all necessary components for a reliable rebuild.
 
Lightweight Design: Reduces reciprocating mass for smoother operation and increased efficiency at high RPMs.
 
Whether restoring engine performance or conducting routine maintenance, the Vertex 1.5 mm piston kit is designed to meet the demands of marine professionals and enthusiasts. 
 
Consistent Compression Ratios: Restores engine efficiency and power output.
Corrosion Resistance: Materials and coatings are marine-grade, ensuring durability in saltwater environments.
Longevity: Reduced wear characteristics and high thermal stability extend the service life of your engine.
 
The Vertex thin ring piston kit combines advanced material science and precision engineering to deliver unparalleled performance and reliability for Mercury V6 2.5L outboard engines. Its high-silicon content, reduced thermal expansion, and enhanced wear characteristics make it ideal for two-stroke applications. Designed to handle the unique demands of marine environments, these piston kits are an essential choice for anyone seeking to rebuild or maintain their engine for peak performance.
 
Compatible with 1991 2.5s or multiple horsepower models produced between 1992 and 2005 with the conversion washer, the Italian Vertex kit ensures a reliable fit and long-lasting operation. Restore your Mercury outboard's power and efficiency today with the proven durability and performance of Vertex pistons.
 
Each Piston Kit includes:
 
Six (6) Top-Guided Pistons (three (3) Port and three (3) Starboard)
Six (6) Slip-Fit Wrist Pins
Twelve (12) Thin (1.5mm) Rings 
Twelve (12) sealed Wiseco Circlips
Higher Transfer Port vs Stock
Forged from aerospace-grade aluminum
Vertex Slip Coating
 
Replaces Mercury OEM Part Numbers: 883062T3, 9737A7, 9737A9, 9737T9
 
Please select:
 
1) Bore size (Standard, .015" over, .030" over)
2) Do you need Conversion Washers
3) Lightened Race Wrist Pins (82 grams)
 
Please contact Mike Hill at 714-697-1716 or mike@buckshotracing.com to discuss the bore size for your run applications before you finish honing. 
 
More about Vertex Pistons:
 
The Mercury 2.5L 2-stroke outboard engine is widely recognized for its power and performance, making it a popular choice for marine applications ranging from high-speed racing boats to recreational watercraft.
 
At the core of its durability and efficiency lies the piston assembly, where Vertex Pistons stand out as a leading choice for enhanced performance. Crafted from high-strength, heat-treated aluminum alloys, Vertex pistons offer a lightweight yet durable solution capable of withstanding the extreme temperatures and pressures typical of 2-stroke engines. P
 
recision CNC machining ensures tight tolerances, optimal compression ratios, and reduced friction, while the molybdenum-disulfide (MoS₂) coating on the piston skirt minimizes wear and ensures long-term durability. The advanced piston ring design enhances combustion efficiency, reduces blow-by, and prevents ring flutter, all contributing to consistent engine performance over time.
 
Vertex pistons deliver several key performance benefits, including increased power output, improved durability, excellent thermal stability, and faster throttle response thanks to their lightweight construction. These pistons are designed as direct replacements for OEM components, available in standard and oversized dimensions to suit various engine conditions.
 
Proper installation, including cylinder honing, piston clearance adjustments, and ring gap verification, ensures peak performance and reliability. Following a recommended break-in procedure, such as varying RPMs and using high-quality 2-stroke oil, further extends the lifespan of the pistons.
 
Choosing Vertex pistons for a Mercury 2.5L 2-stroke engine rebuild offers a cost-effective, high-performance alternative to OEM parts. With their precision engineering, advanced materials, and proven track record in demanding marine environments, Vertex pistons provide long-lasting reliability and enhanced engine performance for both competitive and recreational applications.