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When it is not possible to drain the oil from the
box cooler, one should pump out the engine
sump as good as possible and increase the oil
change intervals to every 50 running hours.
2.1.5
Further recommendations
As the (indirect) cooling by outboard water is very efficient,
keel cooling is without problems. Most important is to
avoid air traps in the piping and additional ventilation of the
pipes can be necessary when bents are not to be avoided
(refer to figure 7).
Figure 7: Ventilating an air trap
2.1.6
Cooling capacity
Using a box cooler the outboard water will bring the
temperature of the engine coolant only 10 up to 15°
Celsius down. The difference between 90° "in" and 80°
"out" (ΔT) is hardly noticeable. So do not conclude too fast
that the system is not working well. When using another
system than the recommended box-coolers one has to be
certain that the cooling capacity is enough. Paint and
fouling on the hull or on pipes along the bottom can reduce
the cooling capacity of the system.
2.2
DRY EXHAUST SYSTEM
2.2.1
General remarks
A dry exhaust muffler system should be as effective in
silencing the exhaust as a wet marine exhaust system
when applying the right mufflers. However noise could be
generated by vibrations in the mufflers and be transferred
to the structure of the ship. Tacit factors like the length of
specific pipe sections could be important. It is very difficult
to take these factors into account.
A dry exhaust system on a boat can generate
noise problems caused by resonance of the
pipes and mufflers.
EN / WhisperPower keel cooling / September 2010
Figure 8: Dry exhaust system
The standard WhisperPower exhaust kit contains the
materials to perform a professional installation. In the kit is
a stainless steel flexible bellow (hose) to prevent vibrations
to be transferred. Also rubbers are supplied to mount the
mufflers flexible. The insulation blanket for the flexible
bellow and the mufflers are also very effective in damping
vibrations. Still it could be that additional measures has to
be taken like an extra clamp in a vibrating section of pipe,
insulation blankets on other parts of the system and
possibly even additional mufflers.
Special care has to be given to avoid water
from outside to get into the system. When the
exhaust is led through the deck or through the
roof of the wheelhouse, measures has to be
taken to prevent rainwater to enter the
system. Special rain caps are available as an
option.
Figure 9. Ways to prevent water to get in
A negative feature of a dry exhaust system is the heat
radiated by its components.
Measures are to be taken to overcome the heat problem:
The exhaust bent to bring the exhaust out of the canopy is
cooled by water. Insulation blankets are included in the
exhaust kit to insulate the flexible bellow and the mufflers.
When a dry exhaust has its outlet on the deck or the roof,
all the pipes inside the ship that can be touched by people,
has to be insulated.
INSTALLATION
7
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