9
Engine Exhaust
SYSTEM COMPONENTS
WARNING
EXHAUST GAS IS DEADLY! The ex-
haust system must be leak-free and convey all
exhaust outside the boat, away from windows,
doors and vents.
Figures 2 and 3 illustrate typical exhaust systems
where the exhaust-water mixer is above the load
water line and Figures 4 and 5 where it is below.
See
Engine Cooling
(Page 6) regarding raw water
connections. The installation must comply with ap-
plicable standards and regulations, including those
of the USCG and
ABYC.
Mufflers, water separators, resonators and siphon
breaks are available as kits from Onan. Muffler kits
include a strainer for the through-hull fitting.
Fitting and Hose Diameters
No fitting or hose section in the exhaust system may
have a smaller inside diameter than the genset ex-
haust outlet.
Exhaust back pressure must be mea-
sured if the total run of the exhaust system is more
than 20 feet (6 meters). Use larger diameter hose if
back pressure exceeds 3 inches Hg (10 kPa).
Exhaust Hose
Use hose that has been approved for wet exhaust
systems. Approved hose and stainless steel el-
bows are available from Onan. Horizontal runs of
hose must slope down at least 1/2 inch per foot
(42 mm/meter) and be supported such that there
are no sags.
The entire run of hose must be accessi-
ble for regular, visual inspections and replacement
.
Hose Clamps
Use two 1/2 inch (12.7 mm) wide stainless steel
hose clamps to clamp each end of each hose.
Muffler
Install the muffler as close a practical to the engine,
observing the following:
1. The length of hose between the genset and the
muffler should be 1 to 5.5 feet (30 to 170 cm).
2. The muffler inlet must be more than 1 foot
(30
cm) below the exhaust-water mixer
3. The muffler outlet hose must rise straight up
from the muffler into a water separator (Fig-
ures 2 and 4) or elbow that turns sharply down
(Figures 3 and 5).
4. When a water separator is use, the base of the
muffler should not be more than 54 inches
(1.4 meter) below the top of the water separa-
tor (Figure 2 or 4 ). When an elbow is used, the
base of the muffler should not be more than
48 inches (1.2 meter) below the elbow (Fig-
ure 3 or 5).
5. The muffler must be mounted such that air can
circulate underneath to prevent condensation
and mold.
Redistribution or publication of this document,
by any means, is strictly prohibited.
