The Buckshot Racing #77 1.5mm Cylinder Head Gasket is a premium replacement for Mercury Marine OEM Part #27-840322, also referenced as 840322-1 and 840322.
 
Designed to fit all Mercury 2.5 Liter V6 2-stroke outboards manufactured from 1991 to the present, this gasket combines the maximum available piston-to-head clearance, exceptional performance, precision engineering for tuners, and cost-effective pricing.
 
Its 1.5mm thickness positions it as the thick and durable choice for various re-build applications, offering versatility to save and run a block that might have been disregarded or tune a block to higher performance standards.
 
Crafted from Victor Reinz AFM material, the gasket ensures exceptional sealing, durability under high thermal and mechanical stress, and corrosion resistance in marine environments.
 
Manufactured in the USA by Cometic Gaskets, the part benefits from rigorous quality control, making it suitable for stock rebuilds, remanufactured engines, decked blocks, and performance-tuned setups.
 
Our 1.5MM Thick Mercury 2.5 Cylinder Head Gasket provides a versatile solution for a range of applications:
 
Remanufactured Engines - The 1.5mm thickness is perfectly suited for remanufactured engines, ensuring optimal clearance, compression and sealing. Its robust design matches or exceeds the performance of OEM parts like the 27-840322 and 840322-1.
 
Decked Blocks - For engines with decked blocks, this gasket maintains the precise compression ratios required to prevent power loss and leaks, delivering consistent reliability and performance for pistons protruding above the deck.
 
Performance Tuning - The thick gasket is a go-to choice for tuners and engine builders looking to modify 2-stroke outboard port timing by adjusting deck height. Its durability allows it to withstand the increased stresses associated with modified and high-performance engines.
 
S3000 & 300 Drag Blocks - This gasket was also a Mercury Racing factory OEM and homologate part for Champ, F1 and Tunnel Boat Racing. NLA part numbers 27-822844T04, 822844-T04, and 525-27-822844-T04
 
The thicker head gasket stands out for its compatibility with remanufactured engines and high-performance builds. Its 1.5mm thickness ensures the most available clearance, sealing and compression for aggressive tuning, decked blocks, and engines requiring specialized performance adjustments.
 
For professionals and enthusiasts, this gasket delivers unparalleled reliability at a price point of $49.50 each, offering significant savings compared to the Mercury OEM Part Number 27-840322 with an MSRP of $76.99. 
 
Includes one (1) 1.5MM Head Gasket; select the quantity of two (2) at check-out if you are installing both heads on the V6. 
 
Here are the available gasket thicknesses we offer and general recommendations tailored to the specific deck height and piston positions of Mercury 2.5L V6 outboards:
 
0.75mm (0.0295"): Designed for Nikasil blocks and race applications, this gasket is ideal for pistons at 0.008" or more below deck height. It ensures tight squish clearance and enhanced combustion efficiency in high-performance setups. Racers familiar with exploring performance limits may achieve even tighter squish clearances.
 
1.00mm (0.0393"): A specialty gasket for high-performance applications, it suits pistons at 0.000" or more below deck height, balancing compression and safety in performance-focused builds. Tighter squish clearances are achievable for experienced racers.
 
1.10mm (0.0433"): Recommended for pistons at 0.004" or less over deck height, this gasket provides safe and effective squish clearance for high-performance applications, with tighter clearances possible for those who push the limits.
 
1.20mm (0.0472"): Ideal for pistons at 0.008" or less over deck height, this gasket ensures reliability and optimal compression in both high-performance and recreational builds. Racers may fine-tune squish clearances further based on experience.
 
1.50mm (0.0591"): This thicker gasket is designed for decked blocks found in remanufactured, re-sleeved, and highly modified engines. It is optimal for tuners raising port timing through decking, or rebuilders salvaging blocks over-decked through years of use, supporting pistons at 0.020" or less over deck height. Tighter squish clearances can be achieved by racers exploring performance boundaries.
 
Contact Mike Hill at mike@buckshotracing77.com or +1-714-697-1716