Operator`s manual
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 a generator
is
put into service. (Refer to
illustration.) Excessive back-pressure will affect the
engine's performance which affects generator AC
power output.
To measure for back-pressure, use a mercury
manometer, a pressure gauge,
or
a water column. A
boatyard
or
marine mechanic should have a
manometer
or
a pressure gauge.
If
the generator set
does not have a tapped hole in its exhaust elbow, one
must be drilled and tapped for a
1/8
inch NPT fitting
in the dry area
of
the elbow.
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
1/8 inch NPT (National Pipe Tap) pipe fitting.
Measure the engine's back-pressure at the exhaust
elbow while the generator is under a full-load.
Refer to the pressure specifications listed below.
Dimension A cannot exceed
39
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
15.6 ounces
PSI
1.0
PSI
Mercury
Manometer
\
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 generator's exhaust system must be separate from any other engine' s exhaust system. 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.
17
WESTERBEKE
GENERATORS