Part Three
EXHAUST
SYSTEMS
CHAPTER 7
Imagine being able to breathe in, but not being
able to breathe out. How long do you think
you would last? Not long! The exhaust of your
engine is quite literally its exhalation. Exhaust
systems get rid of combustion by-product
gases and a substantial amount of waste heat.
Not only does the exhaust piping have to be
properly designed and installed, but it also
must be properly maintained. A poor exhaust
system will rob a boat’s engine of power and
lead to excess and tiring noise, ruined engines,
fires, and flooding—even sinking.
Whether you’re drawing up a new boat or
surveying an old one, installing a new engine
or simply replacing a damaged or corroded
part of an existing exhaust system, it’s criticalthat you check to see that the exhaust system
meets minimum requirements for safety and
efficiency. In this chapter, we’ll examine the
fundamentals of standard and some not-so-
standard wet exhaust installations to give
you a good basis for either laying out a new
system or evaluating or improving an existing
one.
The basic system for a typical sportsfish-
erman or motor cruiser—one with the engine
exhaust manifold well above the waterline—
is shown in Figure 7-1. At first glance, it
seems simple enough: you run a pipe aft from
the exhaust manifold, stick a muffler some-
where in the middle, and that’s that. If only it
were so!Wet Exhaust Systems
Figure 7-1.
Exhaust system