Custom Marine (CMI)

Bridge Spacer Big Tube

CMI 454/502 Direct Mercruiser Replacement E-Top Exhaust System, Polished

The CMI 454/502 E-Top Header Kit is a a true plug and play system. There is no need to purchase additional custom pipes. These are a direct replacement for your stock 454/502 engine. CMI headers offer more water jacketed protection than your stock exhaust can provide. CMI uses the same high quality semi-automated process on these headers as with the entire product line. These headers are fully post annealed to reduce stresses built up in the header during the manufacturing process. Best of all, 454/502 E-Top headers are made to last, they are mandrel bent and formed from hight quality 316L grade material. There are no parts to crack, all CMI collectors are forged from American made Stainless Steel.

Note: All CMI Systems are sold without Talipipes

CMI 454/502 Direct Mercruiser Replacement E-Top Exhaust System, Satin

The CMI 454/502 E-Top Header Kit is a a true plug and play system. There is no need to purchase additional custom pipes. These are a direct replacement for your stock 454/502 engine. CMI headers offer more water jacketed protection than your stock exhaust can provide. CMI uses the same high quality semi-automated process on these headers as with the entire product line. These headers are fully post annealed to reduce stresses built up in the header during the manufacturing process. Best of all, 454/502 E-Top headers are made to last, they are mandrel bent and formed from hight quality 316L grade material. There are no parts to crack, all CMI collectors are forged from American made Stainless Steel.

Note: All CMI Systems are sold without Talipipes

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 this kit, a true plug and play system.

• 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
• Seamless water jacketed header. 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
• Cool collar patented flange design to eliminate the risk of getting water in the motor by the head flange
• 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.

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 this kit, a true plug and play system.

• 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
• Seamless water jacketed header. 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
• Cool collar patented flange design to eliminate the risk of getting water in the motor by the head flange
• 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.

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. The package comes complete with all required mounting hardware plus CMI's exclusive 496 Relocation Kit, which includes all brackets, hoses and hardware needed to make relocation of select engine components easier.

Includes Pneumatic Pump Kit for Internal Sound Choice

Note: All CMI Systems are sold without Tailpipes

ALL CMI HEADERS ARE MADE TO ORDER AND SHIP FROM THE FACTORY IN 7-8 MONTHS

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. The package comes complete with all required mounting hardware plus CMI's exclusive 496 Relocation Kit, which includes all brackets, hoses and hardware needed to make relocation of select engine components easier.

Note: All CMI Systems are sold without Tailpipes
ALL CMI HEADERS ARE MADE TO ORDER AND SHIP FROM THE FACTORY IN 7-8 MONTHS

CMI 520 E-Top Polished Exhaust Header System

• Increases in Horsepower up to 31 HP
• Direct replacement – works with existing exhaust outlets
• Improved mid-range acceleration and torque
• Polished and satin finish available
• Patented “Cool Collar” design
• Mandrel bent and formed from high quality 316L grade stainless steel

CMI 520 E-Top Satin Exhaust Header System

• Increases in Horsepower up to 31 HP
• Direct replacement – works with existing exhaust outlets
• Improved mid-range acceleration and torque
• Polished and satin finish available
• Patented “Cool Collar” design
• Mandrel bent and formed from high quality 316L grade stainless steel

• Increases in Horsepower up to 48 HP
• Downturn collector improves water fill
• Improved mid-range acceleration and torque
• Polished finish available
• Equalized primaries for greater performance
• Patented “Cool Collar” design
• Mandrel bent and formed from high quality 316L grade stainless steel

Note: All CMI Systems are sold without Tailpipes

CMI Big Block Chevy E-Top Polished Exhaust System

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. CMI E-Top systems offer separated exhaust passages with long individual exhaust tube runners to minimize cylinder to cylinder influence and improve exhaust gas scavenging, which allows the engine to breathe freely and deliver peak performance power. Each header features a permanently attached, non-adjustable exhaust tailpipe configured to meet precise specifications for stan¬dard transom layouts and placement of thru-hull exhaust tips. All CMI Elbow Top Systems include rubber water distribution tubes, cooling water bypass couplings installed on the collector elbow, by-pass hose fittings, attaching cap screws, exhaust port gaskets, hose clamps and cooling water inlet fittings needed for most installations.

Note: All CMI Systems are sold without Tailpipes

The picture for this item is shown with a Stainless distribution tree, but this part includes a rubber distribution tree.

CMI Big Block Chevy E-Top Polished Exhaust System

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. CMI E-Top systems offer separated exhaust passages with long individual exhaust tube runners to minimize cylinder to cylinder influence and improve exhaust gas scavenging, which allows the engine to breathe freely and deliver peak performance power. Each header features a permanently attached, non-adjustable exhaust tailpipe configured to meet precise specifications for stan¬dard transom layouts and placement of thru-hull exhaust tips. All CMI Elbow Top Systems include rubber water distribution tubes, cooling water bypass couplings installed on the collector elbow, by-pass hose fittings, attaching cap screws, exhaust port gaskets, hose clamps and cooling water inlet fittings needed for most installations.

This Kit includes an upgrade to a Stainless Steel Water Distribution Tree.

Note: All CMI Systems are sold without Tailpipes

CMI Big Block Chevy Sport Tube Exhaust System, 6" Taller, Polished

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.

The all polished Sport Tube system is offered with a range of exhaust tailpipe options, as well as CMI's Sound Choice™ selectable silencing system. Each system includes all header attaching bolts, gaskets and cooling fittings required for installation.

Note: All CMI Systems are sold without Tailpipes

CMI Big Block Chevy Sport Tube Exhaust System, 9" Taller, Polished

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.

The all polished Sport Tube system is offered with a range of exhaust tailpipe options, as well as CMI's Sound Choice™ selectable silencing system. Each system includes all header attaching bolts, gaskets and cooling fittings required for installation.

Note: All CMI Systems are sold without Tailpipes

CMI Big Block Chevy Standard Bravo Sport Tube Exhaust System, Polished

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.

The all polished Sport Tube system is offered with a range of exhaust tailpipe options, as well as CMI's Sound Choice™ selectable silencing system. Each system includes all header attaching bolts, gaskets and cooling fittings required for installation.

Note: All CMI Systems are sold without Tailpipes

CMI CMI LS Chevy E-Top Headers, Polished or Satin Finish

• Improved exhaust flow over existing cast manifolds
• Lightweight 316L stainless steel
• Increased fuel efficiency
• Inside port size of 1-5/8", also in 1-7 /8"
• Smooth mandrel bent tubes
• No separate tailpipe required
• Taller custom application options

Note: All CMI Systems are sold without Tailpipes

CMI Small Block Chevy Sport Tube Exhaust System, Polished

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.

The all polished Sport Tube system is offered with a range of exhaust tailpipe options, as well as CMI's Sound Choice™ selectable silencing system. Each system includes all header attaching bolts, gaskets and cooling fittings required for installation.

Note: All CMI Systems are sold without Tailpipes

Cooling Jumper Hose, 1" I.D.

Cooling Jumper Hose, 1-1/4" I.D.

Elbow Top Clamp, T-Bolt

Replaces Mercury OEM 54-848885.