Westerbeke 7.6 KW BTD 60Hz Operator's 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 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