Whisper Power M-SC3.5 Installation Manual page 8

INSTALLATION
4 SIPHON BREAKER (AIR VENT)
When the point of water injection is below the waterline,
then -when the engine is stopped -there is a risk that the
cooling water may enter the engine as a result of
siphoning. To avoid this happening, the generating set is
designed to accommodate a siphon breaker (air vent). In
the standard delivery the connections are bypassed. Hose
of 12.5 mm (1/2") inner diameter should be used. If the
generating set cannot be mounted such that the bottom of
the generating set is placed above the waterline, an air
vent must be installed. Extend the water hose of the by-
pass 600 mm above waterline and install an air vent.
Ideally, the air vent should be mounted above the yacht
keel center line (i.e. to minimize the influence of swaying
on the water intake). The hose of the drain should go
downwards. Water must flow out freely and air has to flow
in freely as well (refer to figure 7).
Fast motorboats will lay deeper when sailing at large
speed and can cause pressure on the waterinlet. This
should be avoided to prevent flooding the engine. If the air
vent is clogged the water hoses will not be vented when
the generating set has stopped and water can be forced
into the engine. This leads to immediate engine problems
and eventually severe damage!
DAMAGE CAUSED BY THE INGRESS OF
WATER IN THE ENGINE IS NOT COVERED
BY WARRANTEE.
On the valve is a little hose to drain a little water that could
be spilled from the valve. This hose should go down and
may not end under water, because it should ventilate air
into the valve to break the siphoning (figure 7).
8
Figure 7: Wrong siphon breaker hose routing
Check the air vent at regular intervals. Open, clean and
lubricate the valve as required (figure 8).
Figure 8
September 2010 / M-SC3.5 / EN