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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..foad.
Dimension
A
cannot exceed
39
inches of water.
Back pressure, as measured by a gauge instrument, should
not
exceed the following specifications:
3 inches of mercury (0.104 kg/cm
2
)
39 inches of water in a water column
22 ounces psi
1 1/2
psi
(.099 kg/cm
2
at 4
0
C)
Exhaust System Failures
When the engine's raw water is fed into an exhaust system
so
that the
full
stream of this water strikes a surface.
erosion takes place. This erosion may cause premature failures. The proper design of either a water jacketed
orwater injected ''Wef' exhaust system to prevent this problem requires that the raw water inlet be positioned
so that the entering stream
of
raw water does
not
directJy strike a surface. In addition, the velocity of the
entering raw water stream should be as low as possible. which can be achieved by having inlet fittings as big
in diameter as possible.
The best protection against carbon monoxide poisoning is a daily inspection of the complete exhaust system.
Check for leaks around manifolds, gaskets, and welds. Make sure exhaust lines are
not
heating surrounding
areas excessively. If excessive heat is present. correct the situation immediately. If you notice a change in
the sound or appearance of the exhaust system, shut down the unit immediately and have the system
inspected and repaired at once by
a
qualified mechanic.
Make sure there are no unnecessary objects suspended from any portion of the exhaust lines. Exhaust risers
installed
off
the exhaust manifold
should not exceed Ilbs
in total weight when rigidly constructed. Excessive
weight could cause deflection or distortion of the manifold resulting in damage and/or intemalleaks. Inspect
insulated portions of the exhaust system to ensure there is no deterioration of the insulation.
CAUTION
Prolonged cranking intervals without the engine starting can result in filling the engine-mounted
exhaust system with raw water coolant. This may happen because the raw water pump is
pumping raw water through the raw water cooling system during cranking. This raw water
can enter the engine's cylinders by way
of
the exhaust manifold once the
exhaust
system fills.
Prevent this from happening by closing the raw
water
supply through-hull shut-off, drain the
exhaust muffler, and correct the cause for the excessive engine cranking needed to obtain a
start.
Engine damage resulting from this type
of
raw water entry is
not
a warrantable issue;
the owner/operator should keep this in mind.
17
Westerbeke
Generators
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