Swap out that cooked paper shim for Mercury’s Exhaust Elbow Gasket 27-8M0054712 and keep the big-block 8.2 L EC breathing—and cooling—the way it should. Designed for MCM/MIE engines running single-catalyst manifolds, this OEM multilayer gasket seals the joint between the catalyst manifold and 7-inch riser, stopping exhaust leaks that scorch wiring and letting raw water stay where it belongs.

What makes the factory gasket worth the extra few dollars

• Five-layer graphite / stainless stack-up handles 1,200 °F exhaust pulses without crushing or sticking to the flange.

• Embossed fire rings surround each port, keeping coolant passages isolated from hot gas.

• Laser-cut alignment tabs drop over the 10 mm studs so the gasket seats square—no shifting while you wrestle the elbow.

• Pre-applied silicone bead fills micro pitting on older manifolds; no RTV squeeze-out to clog the catalyst brick.

Swap it during a riser service or whenever you notice a sooty halo at the joint. Ten minutes of careful torquing rewards you with quieter idle, cleaner bilge, and the peace of mind that your 8.2 L’s catalyst is protected by the exact seal Mercury engineers specced.