Dave Gerr - Boat Mechanical Systems Handbook-How to Design, Install, and Recognize Proper Systems in Boats

Chapter 9:Dry Exhaust Systems

Figure 9-6.

Mounting for

expansion

1,200°F (650°C). A single expansion slip joint
at the outlet isn’t enough to accommodate
the substantial expansion and contraction
cycles the exhaust will experience over and
over throughout its service life. Careful
thought must be given to mounting all piping
so it can accept this expansion without dam-
age. This can be accomplished using fairly
standard pipe clamps and parts.
Figure 9-6 shows this principle applied
to the muffler in the basic drystack exhaust
system in Figure 9-1. You can see how the ex-
haust sits on the lower clamp band using lugs
welded to the muffler. The upper clamp band
is attached to the mounting bracket with
bolts in a slot to ensure axial movement is
not restrained. The flexible bellows below
the muffler fastens to the engine and allows

expansion here, as well as allowing for the

engine’s vibration.

You can apply this same approach to all the

exhaust piping, using standard pipe clamps.

Typical pipe clamps are shown in Figure 9-7. All

these clamps (and clamps for mufflers) must

have high-temperature insulating liners or pads

to prevent the exhaust heat from being trans-

mitted to the boat’s structure.

An even better approach is to use pre-

manufactured pipe hangers and fixed points

specifically designed for such exhaust in-

stallations. Rubber Design B.V. (distributed

through Soundown in the United States)

manufacturers a complete series of insu-

lated fixed points and stabilizers that are

designed to insulate from heat and allow

expansion (Figures 9-8, 9-9, and 9-10).

Figure 9-7.

Standard pipe

clamps/hangers