Dry Exhaust System
Dry exhaust systems should be equipped with a muffler (silencer) generally as indicated in Figure 3-1. The muffler should be sized as large as is practicable and designed to ensure maximum sound attenuation with minimum back pressure. Dry exhaust systems may be used for propulsion and generator engines of any size.
Figure 3-1 TYPICAL DRY EXHAUST SYSTEM
Figure 3-2 TYPICAL WATERLOCK SYSTEM WITHOUT MUFFLER
[Wet Exhaust System
Wet exhaust systems may make use of water locks and wet mufflers, or both. Water locks alone may provide sufficient sound attenuation, and are thus suitable for generator engines and smaller propulsion engines. With all wet exhaust systems, care must be taken to ensure water cannot back-siphon into the engine. Depending on the relative height of the waterline, an anti-siphon valve or siphon break may be required (not shown in figures).