Mercruiser Exhaust Systems

A Mercruiser exhaust system specifically serves the inboard marine engine. These systems are generally tasked with removing heated air from the system and absorbing some of the noise that comes during operation. The Mercruiser system also keeps the air clear from fumes and smoke.

What is the difference between wet and dry exhaust systems?

Many boats with an inboard motor are equipped with a water cooling exhaust system from Mercruiser. The motor intakes water to the pipe to cool the pipe and ejects the water through the manifold pipes. In contrast, dry exhaust systems, found on powerboats or fishing and work boats, are air cooled. Based on what they are used for, noise reduction is necessary on these types of boats. They also allow for insulation of the hot pipes as aesthetics are not as important.

What are the parts of an exhaust system?
  • Manifold: The exhaust manifold is a pipe within a pipe that both collects hot gas from the engine into the inside pipe and cools it with the cool water in the outer pipe.
  • Cylinder block: The cylinder block is where combustion takes place to provide power to the motor.
  • Riser: A riser, or elbow, is a cylinder pipe that connects the exhaust manifold to the exhaust hose. The risers take water and air from the manifold and move it out of the system and overboard.
  • Gaskets: The gasket seals the engine tightly to keep water from the motor. Marine gaskets are made of materials that are resistant to corrosion.
What does a Mercruiser marine riser do?

The marine riser from Mercruiser is part of the exhaust system and works in concert with the manifold to make sure the boat runs and the system is cooled. The number of manifolds and risers is usually equal. Risers are vital to the system. The Mercruiser riser provides cool water to cool the engine gasses while also providing a barrier to keep the water from getting into the motor through the manifold.

What are some signs of problems with your exhaust manifold?

The exhaust manifold is exposed to water and can suffer from corrosion. Mercruiser recommends periodic maintenance checks be done on the manifold and riser to make sure the system is in good working order. If any of these symptoms are noticed, take swift action to avoid damage to the engine.

  • The motor becomes difficult to start
  • White smoke spews from the motor
  • The motor begins running roughly