Professional BoatBuilder - December-January 2018

DECEMBER/JANUARY 2018 73

Exhaust Gases and Monitoring

 e importance of keeping exhaust

gases out of the cabin and accommo-

dation spaces cannot be overempha-

sized. Any exhaust leak, whether it’s

from a diesel- or gasoline-powered

engine, is dangerous.  e exhaust

plumbing must be continuously gas-

tight from the engine to the through-

hull discharge, which ideally should be

located at the intersection of the hull

and transom or as far outboard as

practical in the transom. Nothing—no

other exhausts, or deck, HVAC dis-

charge, bilge pump, or other drains—

should be plumbed into this line.

Exhaust runs that discharge through

the hull side should include a de ec-

tor just forward of the exit, to induce

water to  ow away from the exhaust

opening. I’ve encountered cases where

water is forced into an exit, particu-

larly of an engine or genset that isn’t

running, when the vessel is at an

All exhaust system sup-

ports, particularly those with

brackets welded to dry por-

tions of risers, must be ade-

quately insulated or isolated

so they will not become a

burn hazard or ignite nearby

combustible material such as

timber,  berglass, or insula-

tion.  ese too are subject to

the 200°F-threshold guide-

line. I routinely record tem-

peratures in excess of 400°F (204°C)

on brackets without adequate isolation

or insulation under heavy engine

loads.

 exible bushings of an appropriate

hardness for the weight being sup-

ported or sprung brackets for over-

head support.

Risers rigidly attached to an

engine must be supported to

ensure that both move in uni-

son. The struts shown here

achieve this goal elegantly with

adjustable, articulated ball ends.

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ato

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