Mercury - Exhaust Manifold Conversion Kit - Water Rails to Cast Iron Exhaust Manifolds w/o Water Rails - Fits MCM/MIE 496 Mag & 8.1S Engines - 866178A02EXH MANIFOLD CONV 496 8. 1 MZ Upgrading an exhaust system isnt just about performanceits about reliability. The Mercury Exhaust Manifold Conversion Kit (866178A02) is designed to replace outdated aluminum manifolds with water rails, transitioning to a more durable cast iron system that improves exhaust flow and extends the life of your engine. Built specifically for MerCruiser 496 MAG and 8. 1S engines, this kit provides everything needed for a