Westerbeke 12C-TWO Operators Manual And Installation Manual page 21

EXHAUST BACK-PRESSURE
The exhaust discharge hose must be of
adequate size and minimal run to prevent
excessive exhaust back-pressure.
Exhaust back -pressure should be checked
before an engine is put into service.
(Refer to the illustration) Excessive back-
pressure will affect the engine's performance
and the power output.
To measure the engine's back-pressure,
use either a mercury manometer, a water
column, or another pressure measuring
gauge. If the enigne set does not have
a tapped hole in its exhaust elbow, one must
be drilled and tapped for a 1/4 inch NPT fitting.
Measure back -pressure at the exhaust elbow
when engine is running at 3000 rpm. Back-pressure,
as measured by manometer, a pressure gauge, or
water column, should not be over the specifications
listed below.
"
."
"
Ii
~.
Mercury
Manometer
NOTE: Other gauges may be available to test for exhaust back-pressure.
Contact your local Westerbeke dealer.
A water column can be made by taking a
clear plastic tube and taping one end of the
tube along a yardstick and fitting the other
end of the tube with a 114 inch NPT
«National Pipe Tap) fitting.
Measure the engine's back-pressure at
the exhaust elbow while the engine is
running at 3000 rpm.
Dimension A cannot exceed 27 inches of water
Back pressure, as measured by a gauge
instrument, should not exceed the
following specifications:
2 inches of mercury
27 inches of water in a water column \
1.11 kgicm 2
15.60unces per square inch
1.0 psi
Exhaust
Elbow
Exhaust
~~...-
\
Excessive back-pressure can be caused by a small diameter exhaust hose, a small muffler, sharp bends in
the exhaust hose, improper fittings, water pockets, and a high volume of water in the exhaust system due
to the length of the exhaust discharge hose. The use of elbows and fittings in the exhaust discharge hose's
routing should be limited since these will create flow restrictions and contribute to exhaust back-pressure.
The engine's exhaust svstem must be separate from an" other engine's exhaust svstem. Dry portions
of the exhaust system between the engine's exhaust manifold and the water injected exhaust elbow must be
insulated to hold in the heat.
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Westerbeke Engines