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CMI Industrial is proud of its heritage as a designer and manufacturer of top-quality sound and noise attenuation systems that have set the benchmark for quality and innovation. CMI has enjoyed a decades-long leadership position by offering unparalleled products and services, and maintaining industry-leading customer satisfaction.

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The Value of CMI™ Exhaust Headers

CMI Header

Generating the most power possible from a marine engine is a challenge every performance boater faces, whether you’re competing on the race circuit or simply enjoying a day on the water with friends.  Many boaters pursue power increases through a range of aftermarket add-ons: intakes, carburetors, ignitions, water pumps, and valve covers.  However, many continue to run stock, cast-iron exhaust manifolds.  Simply put, design constraints for cast-iron manifolds create internal air resistance making it difficult for exhaust gas to flow freely as it exits a cylinder, which robs the engine of horsepower.  Small exhaust pipes or a muffler that has a lot of air resistance can cause back-pressure, which also has the same effect.

The easiest way to increase horsepower is to enable exhaust gasses to freely exit the engine by installing CMI tubular-style headers, which are designed specifically to improve your engine’s ability to breathe freer and generate more power than stock, cast-iron exhaust manifolds.  Dynamometer testing has proven that "hot" cylinders are a common cause of premature engine failure, especially in high performance marine applications.  The superior design of CMI header systems improve scavenging of each cylinder to remove exhaust gasses that produce potentially damaging high cylinder head temperatures.

All CMI high-performance exhaust systems feature headers, big tail pipes and free-flowing mufflers to eliminate back-pressure in the exhaust system.  Long tubular-style headers, like CMI Sport Tubes and CMI Big Tube headers enable naturally aspirated engines to reach peak power through more efficient exhaust scavenging and improved exhaust tuning.  For blown and supercharged engines, short tube-style headers, like CMI Elbow-Top headers, perform similarly to, and in some applications better than, long tube-style headers.

CMI headers are made from high-quality 316L and 317L stainless steel tubes and heat treated (annealed) for added stress relief and superior durability.  All CMI headers are hand-welded and polished by skilled artisans who are proud of the top-quality exhaust systems they build.  Best of all, every CMI exhaust system is designed to deliver the highest level of quality and peak on-water performance every CMI customer demands.

Choose the Right CMI™ Header System For You.

Choose a CMI™ Header System

CMI Big Tube™ Systems

CMI Big Tube Header

CMI Big Tube headers enable big block engines with 540 cubic-inch displacements or more to deliver peak horsepower and torque throughout the entire operating range. CMI Big Tube Headers are proven to withstand one of the toughest marine environments on earth – offshore racing – and have powered more National and World Championship boats than all other brands combined. CMI “Big Tubes” can be custom stepped in any configuration to meet any engine builders’ requirements. More...

CMI Big Elbow Top™ Race Systems

CMI Big Elbow Top Race Systems

CMI’s Big Elbow Top Race Systems are precision-built for Sportsman-class racers who expect the most from their 510 cubic-inch carbureted engine or 600 cubic-inch engine equipped with a blower package. This race-style header system has a superior track record when it comes to getting to the finish line. Racers participating in APBA, SBI, OSS and USO competitions have found CMI Big Elbow Top Race headers help produce more torque and raw horsepower than any competitive exhaust products. More...

CMI Sport Tube™ Systems

CMI Sport Tube Drop Header

CMI Sport Tubes are a superior long tube header designed for both racing or virtually any high-performance application. For big- and small-block applications where maximum scavenging and horsepower are required, CMI Sport Tube headers deliver peak performance and power from naturally aspirated engines that generate more than one horsepower per cubic inch of displacement. More...

CMI 496 Sport Tube Performance Package™

CMI 496 Sport Tube™ Performance Package

The CMI 496 Sport Tube Performance Package delivers improved performance across the entire operating range of any 496 engine package. When applied to a stock 496 engine, this package will help to increase horsepower, boost mid-range torque, improve fuel economy across the power curve and enhance the engine's overall running quality. More...

CMI Elbow Top™ (E-Top) Systems

CMI Elbow Top Systems

CMI Elbow Top headers are designed for direct replacement of most stock cast manifolds. Top engine builders and stern drive manufacturers who want to optimize performance of small- or big-block marinized engines prefer CMI Elbow Top headers for their engines. More...

Split Top Components

Header Upgrade Garage

  • Brackets
  • Sensor Couplings
  • Header Bolts

Small Block Headers

CMI Small Block Headers

Increase horsepower! Increase torque! Increase fuel economy! CMI's new Small Block Headers are a cut above the rest. These performance headers increase horsepower 10+ and improve fuel consumption. Small Block headers boost mid-range torque by a whopping 15%, giving you an advantage over other boaters. More...

496 E-top Headers

CMI 496 E-top Headers

Direct Mercruiser replacement for your 496 Mag or 496 HO engine. No additional custom tails to buy. You don't need to remove your stock exhaust hose to install our kit, a true plug and play system. This kit is Price competitive to other aluminum/stainless manifold systems with superior performance and extended life span in harsh marine environments. More...

Gen-X Headers

CMI Gen-X Headers

Direct factory replacements for Merc 525 to 700 engines.

Works with existing tailpipes. Quality 316L Domestic Stainless Steel. More equalized primaries for improved performance. Improved water fill to help the header last longer in harsh environments. More...

520 Headers

520 upgrade package

Horsepower gains from 31hp to 48hp!


Evo-X Headers

Evo-X Headers

1100HP/1350HP/1550HP/1650HP CMI stainless steel headers!


LS E-Top Headers

LS E-Top Headers

New LS E-Top Small Block headers for superior exhaust performance