The Buckshot Racing #77 10-Piece Race Head Gasket Bundle is built for Mercury 2.5 Liter V6 two-stroke owners who need to tune compression, control squish clearance, and match head gasket thickness to piston deck height without immediately changing cylinder heads.
 
This kit is designed for select 1991–2005 Mercury and Mariner 2.5L V6 two-stroke outboards, including many 135 HP, 150 HP, 175 HP, 200 HP, 225 Pro Max, 260 ROS, 300 Drag, XR6, and SportJet 175 HP powerheads using the compatible gasket-head 2.5L configuration.
 
For racers, engine builders, and performance tuners, head gasket thickness is more than a sealing choice. It directly affects combustion chamber volume, compression ratio, piston-to-head clearance, squish behavior, detonation margin, and overall engine consistency. This gasket bundle gives builders several thickness options so they can fine-tune setup during assembly, testing, or class-rule preparation.
 
Built for Compression and Squish Tuning
 
Many high-performance Mercury 2.5L engines are assembled around a target compression number or minimum piston-to-head clearance rule. Instead of cutting heads every time a change is needed, builders often use head gasket thickness as a practical tuning tool.
 
A thinner gasket can increase compression and tighten squish clearance, while a thicker gasket can reduce compression, add clearance, and improve safety margin when pistons are near or above deck height.
 
This kit is especially useful for outboard drag racers running compression-limited classes in organizations such as SODA, ODBA, DSRA, and UMPBA, as well as tunnel boat and Formula-style racers working within squish or combustion chamber rules in APBA, OPC, F1H2O, AFPGP, and similar competition environments. It is also valuable for lake racers, performance tuners, and engine builders assembling modified or freshened Mercury 2.5L Pro Max, ROS, Drag, XR6, EFI, and carbureted V6 engines.
 
Premium Gasket Materials
 
This bundle uses performance gasket materials selected for demanding two-stroke marine use. The 0.75mm and 1.00mm head gaskets are made with Athena M0115, an Italian high-performance gasket material featuring an asbestos-free composite construction built around a pegged steel core. This construction provides strength, dimensional stability, and sealing performance in high-load engine applications.
 
The 1.10mm, 1.20mm, and optional 1.50mm gasket thicknesses are produced from Victor Reinz AFM material, a premium German-engineered fiber-reinforced elastomeric gasket sheet made with aramid fibers, mineral fillers, and rubber-based elastomers. AFM-style gasket material is widely used in high-performance engine sealing applications where heat resistance, compressibility, and stable sealing are important.
 
What Comes in the 10-Piece Bundle
 
This 10-piece Mercury 2.5L race gasket bundle includes matched pairs and additional tuning sizes for common racing and rebuild combinations:
 
2 x 0.75mm head gaskets — approximately 0.0295" thickness
2 x 1.00mm head gaskets — approximately 0.0393" thickness
2 x 1.10mm head gaskets — approximately 0.0433" thickness
4 x 1.20mm head gaskets — approximately 0.0472" thickness
 
Optional 1.50mm gaskets are also commonly used in Mercury 2.5L setup work when additional clearance is needed, especially on engines with pistons farther out of the deck or builds requiring lower compression.
 
Head Gasket Thickness & Suggested Clearance Reference
 
For practical engine-building reference, Buckshot Racing #77 uses the following gasket thickness guide when matching head gasket selection to piston deck height and piston-to-head clearance targets.
 
0.75mm, approximately 0.0295", is commonly suggested for pistons at 0.008" or more below deck height.
1.00mm, approximately 0.0393", is commonly suggested for pistons at 0.000" or more below deck height.
1.10mm, approximately 0.0433", is commonly suggested for pistons at 0.004" or less over deck height.
1.20mm, approximately 0.0472", is commonly suggested for pistons at 0.008" or less over deck height.
1.30mm, approximately 0.0512", may be used in setups where additional clearance is needed beyond the 1.20mm range.
1.50mm, approximately 0.0591", is commonly suggested for pistons at 0.020" or less over deck height.
 
This chart is a practical reference only. Final clearance must always be measured during assembly. Piston rock, rod length, crankshaft stroke, block machining, head machining, gasket crush, combustion chamber shape, fuel quality, timing, and operating RPM all affect the correct final setup.
 
Mercury 2.5L Fitment and Applications
 
These outboard cylinder head gaskets are intended for select 1991–2005 Mercury / Mariner 2.5 Liter V6 two-stroke gasket-head powerheads. Common applications include many 135 HP, 150 HP, 175 HP, 200 HP, 225 Pro Max, XR6, 260 ROS, 300 Drag, and SportJet 175 HP engines using the compatible 2.5L head gasket pattern.
 
They are commonly used on Mercury performance builds, carbureted V6 engines, EFI engines, Pro Max lake motors, drag engines, ROS applications, and modified 2.5L outboards where compression and squish clearance need to be matched carefully. Always verify fitment by engine serial number, block type, head style, bore size, and original gasket configuration before ordering.
 
Part Number Cross References
 
Common Mercury, Sierra, Mallory, and aftermarket cross-reference numbers associated with this gasket family include 18-3864, 184721, 35870, 822844, 822844T04, 822844T05, 822844004, 8228441, 8228442, 8228443, 9-63854, 814658-1, 822844-1, and 27-840322-1. Thickness-specific references may vary by manufacturer, material, and production style, so gasket thickness should always be confirmed before assembly.
 
Buckshot Racing #77 Tech Tip
 
For race classes with compression rules, use this gasket bundle as a tuning tool during setup and testing. For performance lake engines, use it to create a safe and consistent combination that matches your fuel, timing, porting, and intended RPM range.