Professional BoatBuilder - December-January 2018

72 PROFESSIONAL BOATBUILDER

BEST PRACTICES: Exhaust

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section, which absorbs the di erence

in movement between a so -mounted

engine and the vessel’s structure.

Large, heavy systems should

include shock mounting to prevent

vibration from being transmitted to

the vessel’s structure. Choose either

a very  exible section, o en silicone

“hump” hose.

Larger, longer exhaust systems that

are suspended from the overhead and

do not move in unison with the engine

must include a  exible, metallic, typi-

cally corrugated “wrinkle belly” pipe

Additional supports will be

necessary for all but the shortest

engine-manufacturer-supplied

exhaust risers. Choose those

that utilize screw thread adjust-

ments and articulating heads.

Avoid supports that rely on

tube stock with  attened ends;

they are prone to cracking and

are virtually impossible to size

with the precision required to

ensure proper  ange loading.

Ideally, because most engines

are so -mounted (and move

independently of the vessel),

such supports are attached to

the engine or transmission; this

ensures that the entire rigid metallic

exhaust riser/mixing elbow/engine

assembly moves in unison when the

engine vibrates or shi s gears.  e

transition from the engine-supported

metallic exhaust to the wet exhaust,

attached to the hull, should be with

Far left—Dry-exhaust-

component misalign-

ment, or inadequate

support, can lead to

catastrophic and

costly failures of the

system. Left—Tube

stock with  attened

ends, which are prone

to stress failure and

not easily adjustable,

is a poor choice to

support metallic risers.

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