We offer a selection of 2.5-liter high-performance cylinder head gasket thicknesses that fit all 1991 - Present gasket-head Mercury / Mariner 2.5 Liters; XR6, 150 HP BB, 175HP CC, 200HP EE, 200HP FF, 225HP NN, 245HP KK, 260 ROS, LL, PP, SS blocks for all recreational sky, tournament bass fishing, outboard drag racing, and USF1 & F200 race 2-stroke powerheads to increase compression and performance.
 
In a Mercury 2.5L V6 2-stroke at zero deck and a 3.500" bore, head gasket thickness directly affects compression by altering combustion chamber volume.
 
A thin 0.0295" (0.75 mm) gasket adds just 4.65 cc, while a 0.0393" (1.00 mm) gasket contributes 6.20 cc. Thicker options like 0.0433" (1.10 mm), 0.0472" (1.20 mm), and 0.0512" (1.30 mm) increase volume to 6.82 cc, 7.44 cc, and 8.06 cc, respectively. The thickest commonly used, at 0.0591" (1.50 mm), adds 9.32 cc.
 
Thinner gaskets raise compression and improve combustion efficiency, while thicker ones reduce compression and are often used for detonation control or when pistons protrude slightly above the deck.
 
We use Athena M0115 material on our 0.75MM and 1MM head gaskets and Victor Reinz AFM material on our 1.1MM, 1.2MM, and 1.5MM head gaskets.
 
Athena M0115 is a high-performance gasket material manufactured in Italy, designed for demanding engine applications. It features an asbestos-free composite construction built around a pegged steel core, which adds structural strength and dimensional stability. 

Victor Reinz AFM is a premium German-engineered gasket material widely used in OEM automotive and marine applications. It is a fiber-reinforced elastomeric sheet composed of aramid fibers, mineral fillers, and rubber-based elastomers. 
 
Head Gasket Thickness & Suggested Clearances
 
0.75mm (0.0295" thickness) is suggested for pistons at .008" (or more) below deck height
 
1.00mm (0.0393" thickness) is suggested for pistons at .000" (or more) below deck height
 
1.10mm (0.0433" thickness) is suggested for pistons at .004" or less over deck height
 
1.20mm (0.0472" thickness) is suggested for pistons at .008" or less over deck height
​​​​​​​
1.30mm (0.0512" thickness) for pistons at .011" or less over deck height (available upon request)
​​​​​​​
1.50MM (0.0591" thickness) is suggested for pistons at .020" or less over deck height
 
Racers who have explored the limits may be able to run tighter squish clearances.
 
Part Numbers:
814658, 8146581, 18-3864, 184721, 35870, 822844, 822844T04, 822844T05, 822844004, 8228441, 8228442, 8228443, 9-63854, 814658-1 0.75, 822844-1 1.00, 27-840322-1 1.50
 
Includes one (1) cylinder head gasket for a Mercury 2.5 Liter Outboards.
 
The V6 powerhead requires two (2) gaskets if both heads are removed. Order the number of head gaskets needed and select your thickness before checkout.
 
Contact Mike Hill at +1-714-697-1716 or mike@buckshotracing77.com with any questions or to discuss the right head gasket thickness for your motor.