Westerbeke 6.5KW Technical Manual page 12

must always be above the water line at all angles
of
vessel operation to prevent siphoning. The vent, when
used, must have its vent hose or tube routed so as to be above the water line and to remain empty of water
when the engine is shut down to allow air to enter through this vent and prevent siphoning.
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 to a gen-
erator is put into service. (Refer to the illustration.) exces-
sive back-pressure will affect the engine's performance and
the generator's power output.
To measure the engine's back-pressure, either a mercury
manometer, a water column, or another pressure measur-
ing gauge has to be used. If the generator 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 the engine's back-pressure at the exhaust elbow
while the generator is under a full load. Back pressure, as
measured by a gauge instrument, should not exceed the fol-
lowing speCifications:
3 inches of mercury (0.104 kg/cm
2 )
39 inches of water in a water column (.099 kg/cm
2
at 4
0
C)
22 ounces psi
11/2 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, 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 sys-
tem between the engine's exhaust
manifold and the water injected ex-
haust elbow must be insulated to
hold in the heat. Dry stack type ex-
haust systems must be attached to
the generator engine's exhaust
manifold by means of a flexible
connector pipe. This system must
be properly supported and insu-
lated to prevent water entry into the
engine's cylinders. Provisions
must be made for the discharge of
the engine's cooling sea water.
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II
Dry Stack Exhaust