DeAngelo Marine’s Basic Rules For Exhaust Systems


Designing a marine exhaust system for a boat is something that apparently takes the back seat during the planning stages when doing a repower.

In new boat construction, the design of many systems seems to center around the “cookie cutter” philosophy, as builders always seem to want to or work around a factory designed wet elbow system that is supposed to “fit all”. Besides that, many new builders are more concerned about getting the engine below a low deck than worrying about the exhaust and exhaust outlet of the engine being close, at, or BELOW the water line.

Basic Rules For Exhaust Systems

Cardinal Rule #1 – Wet Exhaust Height Above LWL. Remember this as the “spill-over” point

  • Understand the difference between a “requirement” and a “recommendation” from the engine manufacturer regarding exhaust design.
  • Always use gravity to your advantage.
  • Always use all of the available height in the engine room for the riser (where needed and is practical) BEFORE turning over the top and injecting water.
  • Be sure that IF the option presents itself in the design of a wet exhaust system, allow for all of the water to drain itself from the exhaust when not running.
  • When using a “lift muffler” design, remember that in most cases you can make the system “inherently safe” by being sure that the engine “spill-over” height is higher than the lift muffler spill over point.
  • Overall Exhaust design can usually be made better in many ways if you DO NOT use “cookie cutter” type exhaust components.
  • Never, never, never do you want a boat that has saltwater cooled wet risers or pipes unless they are installed in such a manner that when they leak they are downhill of the engine “spill-over” point.
  • When the vessel design is such you are very limited as to the physical dimensions of the exhaust size ( like installing a muffler in a confined space) and you need to reduce back pressure but you cannot install larger pipes, tubes, etc, another option would be to bypass some of the water that is normally mixed into the wet exhaust.

There are a number of “rules for exhaust” that we may use as guides when designing and engineering systems for marine applications.

DeAngelo Marine Exhaust Systems Contact DeAngelo Marine if you require an inspection / survey of your engine room, main engines or generator exhaust systems. We invite your inquiry for exhaust parts & accessories and exhaust repairs and service with your existing vessel. If you are in the design phase of new vessel construction or contemplating an engine overhaul, contact DeAngelo Marine Exhaust by email or by telephone: +1 954.763.3005.

2017-04-24T20:58:29+00:00 Design & Engineering|