Custom Marine Inc.

Neenah,  WI 
United States
  • Booth: 622

Choose CMI...You'll Be In Good Company!

For more than two decades, Custom Marine stainless steel exhaust systems have been skillfully-built to exact standards.  This has made us the number one choice for offshore racers and performance-oriented boaters who demand superior on-water performance.  CMI offers performance stainless steel water jacketed exhaust headers, tailpipes, diesel exhaust risers, mufflers, sea strainers, other exhaust components as well as machining and brake press capabilities.  Common material used is 316/304 stainless steel, duplex 2205, titanium and aluminum.  

At CMI, we work with the most respected marine engine manufacturers, OEM boat builders and distributors in the world who place their trust in CMI to ensure their products deliver the performance and quality their customers demand.

Our industry-leading technologies and race-proven products have earned us a place in the winner’s circle on race circuits worldwide. But it’s our reputation for delivering high-quality performance products that has earned long-term relationships with the customers we serve.


  • 496 E-Top Headers
    CMI's 496 E-Top Headers are a direct Mercruiser replacement for stock 496 Mag or 496 HO engines.


    • 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 new kit introduces CMI’s new low cost satin finish. For an additional charge you can have our classic high polished stainless finish.
    • 1 7/8" id primary to get peak horse power and torque.
    • Mandrel bent and formed from High quality 316L grade material.
    • Fully post annealed to reduce stresses built up in the header during the manufacturing process
    • The only seamless water jacketed header manufactured. No welded inner primaries or water jacketed tubes to crack and leak.
    • More water jacketed protection than your stock exhaust.
    • Approved by Mercruiser to not void warranty on the motor, with the exception of water reversion.
    • Same high quality semi automated welding as used on all racing applications
    • Patented “Cool Collar” design provides a short hot section at the flange, which helps minimize the possibility of water ingestion in to the engine.
    • This kit is price competitive to other aluminum/stainless manifold systems with superior performance and extended life span in harsh marine environments.
    • No cast parts to crack, all CMI collectors are forged from American made stainless steel.
    • Works on 34.5" drive centers
    • Brings a race look to your stock engine.
    • Sophisticated engineering leaves your stock oil lines in place and only requires relocating your oil filter with a supplied bracket.
    • Step by step, do it yourself instructions using Mercury supplied engine schematics.
    • Exhaust Water Temperature Bungs Installed as Standard Equipment.
  • GenX Headers
    A direct factory replacement for Mercury HP525 EFI, HP600 SCi and HP700 SCi engines....

    • Downturn collector provides improved water fill.
    • More equalized primaries for greater performance in horsepower and torque.
    • Using the same high quality 316L stainless steel that is used in our race systems.
    • Patented “Cool Collar” design provides a short hot section at the flange, which helps minimize the possibility of water ingestion in to the engine.
    • Dual bolt pattern for both the Mercury platform and the standard GM pattern.

  • LS Small block Headers
    New LS E-Top Small Block headers for superior exhaust performance...

    • Port sizes available in 15/8" and 17/8" i.d.
    • Polished or satin finish 316L stainless steel for corrosion resistance and durability
    • No separate tailpipes required
    • Custom applications available
    • Patented “Cool Collar” design
    • Hand-welded and fabricated by skilled craftsmen
    • Made in the USA
  • XTS™ Exhaust Tip Silencers
    CMI offers a complete line of silencers and mufflers to fit most high performance exhaust system applications....

    • Engineered to reduce sound without creating unwanted backpressure
    • 316L Polished Stainless Steel
    • Smoother tone in all speed ranges
    • Available in “Tip-style” or “Clamp-on”
    • Water acts as a noise deadening medium
    • Fully Passivated to minimize ugly rust streaks on the transom

Send Email

Type your information and click "Send Email" to send an email to this exhibitor. To return to the previous screen without saving, click "Reset".

For Technical Support with this webpage, please contact support.