Mercury Racing's exclusive X-Haust Noise Reducer features a fully integrated sterndrive exhaust noise reduction system. X-haust was developed primarily to bring the HP600 SCi and EU662 SCi sterndrive engine packages, already certified by the European Union Recreational Craft Directive (RCD) requirements for exhaust emissions, in compliance with the stringent RCD noise regulations.
To develop this system, Mercury Racing employed predictive simulation in the X-haust design. This allowed the engineers to model characteristics of the engine and predict the pressure waves the engine creates through the exhaust system. After adopting a basic design idea, several iterations were applied until the muffler was perfectly sized and the required sound attenuation was achieved.
X-haust features a custom Y-Pipe which combines the two banks of exhaust from each engine into a single exhaust tube. The single tube exhaust outlet per engine provides the transom space needed for the transom mounted X-haust muffler. An integrated idle relief tube routes some exhaust through the boat above the waterline, providing a necessary vacuum break and a little rumble when operating off plane.
Stage 1, designed to satisfy most noise regulations outside of the EU, eliminates the transom mounted mufflers. The exhaust outlet remains in the same location – underwater when off-plane and near the water surface when operating on-plane. Stage 2 is the complete system, with transom mounted mufflers, capable of compliance with the EU RCD.
