The Mercury OEM Cylinder Head 8M0143213 is a factory replacement head for many legacy Mercury Marine, Mariner, and Mercury Racing V6 two-stroke outboards that use gasket-style heads.
These are widely considered the last production run of the classic “top hat” combustion chamber gasket heads. You will also see them identified by the casting number 18488-C5 and the other superseded numbers listed below in parts lookups and on the head itself. The 18488-C5 casting is a key identifier for this head family.
These heads are commonly used on engines built from 1991–2005, including 150 HP, 175 HP, 200 HP, and popular models such as Mercury XR6, 225 Pro Max, 245 HP carb, and 260 EFI.
Because many motors have been rebuilt or modified, the most reliable confirmation is matching your parts diagram to 8M0143213 and verifying your engine uses a head gasket.
What the cylinder head does
The head forms the combustion chamber roof, seals the cylinder with a head gasket, and transfers heat into the cooling system. A flat, crack-free head with correct torque supports stable compression, temperature control, and reliable sealing—especially on higher-output 2.5L platforms.
“Top Hat” combustion chamber heads
“Top Hat” refers to the chamber profile used on these late gasket heads. Many builders prefer this later OEM style for its proven gasket-head configuration. For a correct OEM replacement, 8M0143213 / 18488-C5 is the go-to gasket head.
Fitment: common model names (1991–2005)
Common applications include legacy 2.0L and 2.5L V6 engines in 150/175/200 HP families plus performance names like XR6, 225 Pro Max, 245 Carb, and 260 EFI. The best range of Mercury 2.5 Liter Head Gaskets is available on our website.
Cross-references and legacy numbers
Catalogs may list 8M0143213 alongside earlier numbers such as 184883, 184884, 184885, 184886, 184888, 184889, 18488A1, 18488C4, 18488C5 (18488-C5), 18488F1, 18488F2, and 1848810.
Installation notes: torque and sequence
Clean surfaces, use the correct head gasket, and torque evenly. A commonly used target torque for these heads is 30 ft-lbs, tightened in steps. The torque sequence is marked on each head, making it easy to follow the correct pattern. For modified engines or non-stock fasteners, confirm procedure with your Mercury service manual or builder.
Contact Mike Hill at +1-714-697-1716 or email mike@buckshotracing77.com for technical support.