Westerbeke BCD 4.4KW Operator's Manual page 25

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 gener-
ator is put into service. (Refer to the illustration.) Excessive
back-pressure will affect the engine's performance and the
generator's 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.
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.
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 1/4 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.
Dimension A cannot exceed 39 inches of water.
Back pressure, as measured by a gauge instrument, should
not exceed the following specifications:
Specifications:
2 inches of mercury
27 inches of water in a water column
15.6 ounces PSI
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 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.
Westerbeke Generators
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