Sierra 18-1976-2 MerCruiser V6V8 GM 2002 Older Manifold Elbow Replaces 807988A03 Unlike automotive engines, all marine inboards have exhaust risers that feature a water induction elbow. Located behind the engines coolant reservoir, the manifold elbow is a critical component to prevent water from entering the engine. It is also a target for corrosion and must be examined frequently and replaced as needed. Sierra, a leading aftermarket manufacturer offers the 18-1976-2 MerCruiser Manifold Elbow w