In the
picture above, the engine is directly
cooled by outside water sucked-in by the
waterpump. The water is cooling the cylinder and
cylinder head where the heat is concentrated.
When the engine is not on operating temperature,
a thermostat within the cirquit is closed and the
water is going out to the exhaust immediately.
Because the
engine is located under the waterline, there is a
risk that the cooling circuit will float the
cilinder via the exhaustport (A). Therefore a
airvent (B) is located behind the cooling outlet,
far above the waterline.
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| On the left site you see
the point where the cooling inlet is poking
through the hull. I fixed it with glassfiber and
epoxy. The inletscoop on the outside always must
point backwards, otherwise, when sailing with an
idle engine, a positive waterflow into the port
will cause water pressure and possible floatation
of water into the engine cylinder. For safety
precautions, the inletport must be fitted with a
valve (left). From the inlet the water is going
to a filterunit (right). |
| The cooling
water strainer (right) has a transparent cover,
allowing easy inspection of the filter without
dismantling. The cleaning of the filter will take
only 30 seconds. Due to the large active surface,
the filter seldom needs to be cleaned. According
to the manufacturer, the filter always has to be
placed above the
waterline. When the cover is not tightly closed,
air will be sucked in by the cooling pump. This
can cause overheating of the engine. Therefore,
the engine manufacturer advises to install the
filter under the
waterline ! And that's what i did. Annual
inspection of the filter and the hoses is needed
anyway. |
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Like a human
hart, when the waterpump stops there is no
cirquilation. Therefore it must be kept in
perfect condition. Driven by the engine, a rubber
impeller behind the round coverplate is pumping
water into the engine's cylinderhousing. During
wintertime the impeller must be removed for
inspection and stored seperately. If the impeller
has no visible wear and tear it can be re-used at
the start of the new season. Good practice is to
use some grease before putting it in again. Never
forget to open the inlet valve before starting
the engine, otherwise the impeller will burn away
in a few seconds. |
| On the left you see an
inside scetch of the thermostat pictured on the
right. The cooling water flows into the engine
and is heated. The engine feeds hot water from
below. When heated, the spring valve releases and
the hot water can leave the engine. The
thermostat is opening at a fixed temperature
(operating temperature). Excess cooling water
provided by the waterpump flows from
left->right over the top. On the right side
the water is leaving to the exhaust system . With
an open cooling system as pictured above, the
thermostat housing can be clogged by mud. It is
recommended to connect the sensor on the
thermostat housing to a manufacturer approved
temperature indicator on the operator panel |
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Eventually,
the coolingwater leaves via the airvent. When
there is no flow, the water level drops because
on the top is an opening where air can come-in. Water can also leave on top of the
airvent when the engine is running. This water
needs to be disposed of via a small opening
through the outside hull.
PS: recently the
ventilation hose brake loose. Within no-time i
had thirteen buckets of cooling water in my boat.
I recommend to replace all original plastic hose
clamps (see photo) with industrial steel
hoseclamps like those on the lower hoses (left)
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