Alpha Male-Ness Without All The Barking

Mercury wants (and is required) to have exhaust and noise emissions compliant propulsion. By being responsible citizens (you and us), our freedom on the water can continue. Global regulations have caused larger marine engine manufacturers to invest millions of dollars in research and development. In that work, Mercury developed an on-board microprocessor that controls all aspects of engine operating performance – including fuel management and exhaust emissions.  The combination of advanced engine components (hardware), fuel calibration development (software) and extensive testing (more hardware and software) led us to a full line of sterndrives that meet U.S. California Air Resources Board (C.A.R.B.) and Environment Protection Agency (EPA) regulations.  But, as we have learned with experience, emissions regulations are ever evolving.

X-haust Noise Reducer logo: noise in, X, quiet out.
Baja 35 Outlaw with twin 662 SCi’s and X-haust.

Just when we thought our job was done, by meeting the CARB and EPA regulations in place at that time, more stringent ones were being implemented by the European Union (EU) Recreational Craft Directive (RCD). We had to do additional work to create “global” engines that would meet stringent EU RCD exhaust emissions and noise regulations.

We tackled exhaust gas emissions first. The EU662 SCi is he highest horsepower we could attain and still meet the EU RCD exhaust emissions regulation. Also, we were able to adjust fuel calibration on the 600 SCi to make it RCD exhaust emissions compliant.

Then, noise.  Engines, as rigged with a typical through transom exhaust system, didn’t pass RCD noise requirements. Aftermarket mufflers didn’t help. Running exhaust through the prop isn’t an option with our engines: too restrictive.

Stage 1 X-haust Noise Reducer system for staggered engines. The forward drive-line engine features optional straight headers.

Our solution was a fully integrated sterndrive exhaust noise reduction system — designed specifically to bring the 600 SCi and 662 SCi  into compliance with the stringent RCD noise regulations. Our X-haust Noise Reducer system features a custom y-pipe. It combines the two banks of exhaust from each engine into a single exhaust tube that exits the transom below the water line. An integrated idle relief tube routes some exhaust through the boat, above the waterline, providing a necessary vacuum break.  This is referred to as “Stage 1” X-haust. This configuration is sufficient to meet most noise regulations outside of the EU.

A side-by-side close-couple installation featuring the Stage 2 X-haust Noise Reducer system.

The EU RCD noise test requires the boat to pass a sound meter at a distance of 25 meters (82 feet). The boat must be traveling at least 70 kph (43.5 mph), but need not be at maximum speed. To pass the regulation, the average of the two highest results cannot exceed 78 dBA.  78 dBA is quiet! As a point of reference, we measured the sound of water lapping the shore at 75-80 dBA.

Stage 2: To meet the stringent EU RCD noise emissions requirements, Mercury Racing engineers designed a transom mounted muffler which is perfectly sized to achieve the required sound attenuation. The muffler design, connected to the Stage 1 X-haust transom outlet, flows exhaust through two separate chambers connected by three attenuator tubes before exiting the exhaust outlet at the bottom.

This cut-away of our Stage 2 X-haust muffler shows its two chambers connected by three attenuator tubes.

The result is further reduction of sound pressure waves without sacrificing power or performance. The transom mounted muffler is completely submerged when the boat is at rest. The muffler outlet directs engine exhaust down and back toward the transom, further reducing noise. We call this complete system, with mufflers, Stage 2 X-haust.

The new X-haust sweeper header kit allows for the use of factory installed sweeper headers on the forward drive-line engine. The sweeper header X-haust system is backed by a 1-year warranty.

An optional X-haust sweeper header kit has been developed for drive-line engines. The kit includes a revised tailpipe designed specifically for the Mercury Racing sweeper headers. The optional drive-line sweeper header kit is available for all Mercury Racing 502 engines to accommodate the use of the Stage 2 X-haust system.

We make X-haust for use with 525 EFI and 600 SCi engines fitted with an Integrated Transom System (ITS) Bravo One XR drive or  NXT1 drive options, EU662 SCi and 700 SCi sterndrive engine packages fitted with dry-sump NXT1 and 6 SSM drives. Various Stage 1 and Stage 2 configurations will fit either single or twin engine applications – in both side-by-side and staggered installations (with the port engine forward).

There you have it. You can enjoy your time on the water without the hassle of noise police or upsetting the neighbors.

Share Share

11 thoughts on “Alpha Male-Ness Without All The Barking”

  1. Hi. My name is Gustav and I´m from Sweden. I have an odd question but is the “Baja 35 Outlaw 662 SCi X-haust validation test boat” for sale?

    That is the boat of my dreams with those engines (as I live in EU) and the X-haust system which combined with those blowers makes the best noise in history!

    If the test boat happens to be up for sale please let mi know!

    Best regards
    Gustav Selander

    1. Sorry, Gustav. We retire our test boats to the graveyard. Anyway, the test boat pictured is a 29 Baja single 662SCi. Probably not what you want. Sorry for my caption error.

  2. Thanks for the answer !
    The boat that now is called “Baja 29 Outlaw 662 SCi X-haust validation test boat” is in fact a 35.
    I happens to have a 29 at the moment and the boat pictured is a 2006-> design and it has 4 electric bolster seats so it can only be a Baja 35 Outlaw.
    You didn´t have any caption error, it was right the first time! 🙂

    Do you know if the 35 has been past on to meet his maker?! If not I really are interested in bying that boat. I want it all white and I´ve never seen one like that before and is it not better to sell the boat to a Swede than destroy it?

    Gustav Selander.

    1. Sorry, Gustav. Two bolsters up front and a bench in the back. 29 feet. Single 662SCi with X-haust. It is shrink-wrapped and hybernating for Wisconsin’s winter, out behind our engineering laboratory.

      It’s a test mule built for us when Baja was part of Brunswick Boat Group. Trust me. When we retire this, you don’t want it. I like Swedes. Why would I want to hurt one?

        1. Hi Rob:

          We discontinued the 662 SCi at program year, or July 1. The 520, 540, 565 600 SCi and 1100 are all EU emissions certified.

  3. Ok but then maby it´s not the boat I´m asking for.

    I´m interested inte the boat pictured above the “Baja 29 Outlaw 662 SCi X-haust validation test boat” -text and in the video about the x-haust system along with a Fountain 38.

    That boat is a Baja 35 Outlaw.

    1. Don’t worry, Gustav. I applaud tenacity. I also applaud accuracy and you got me thinking.

      The boat you love was not Racing’s Baja 29 validation boat. It was a customer’s Baja 35 Outlaw. (Your eyes are better than mine.) Racing validated the X-haust system in our single engine 662SCi Baja 29. The first twin 662SCi X-haust certification was done in the 35 pictured above – which you correctly identified as a 35. (I know we don’t own a 35 and our 36 is also a single engine, but has only had big power. That is why I believed you were talking about our 29. Sorry about the confusion.)

      Truly, you do not want our 29 Baja. The boat you so desire was sold by Baja to European customer. Perhaps he is following this blog and will contact us or you. If that happens, I will let you know. (Re OSO: I have not been mocking you. Not my style.)

      1. Ok then I understand. I didn’t know about the 29/single 662 so that straitens a few things out 🙂

        I Thought we were talking about the same boat all the time. Bad for Me that 35 was sold. Amazing engine setup!


        1. Let’s hope the current owners of Baja will build more 35s with the 662 setup – maybe one for Sweden’s Gustav Selander!

Leave a Reply

Your email address will not be published. Required fields are marked *