Seawater System; Draining The Seawater System; Check And Change The Zinc Anodes; Seawater Filter Check/Change - Volvo Penta D25A MS Operator's Manual

Maintenance: Seawater system

Seawater system

The seawater system is the engine's external cooling system. It cools the internal cooling system in an engine
mounted or externally mounted heat exchanger. The system is protected against galvanic corrosion by zinc ano-
des located in the heat exchanger.
WARNING! The seawater cocks and/or the cocks of the external cooling system must be closed before
commencing work on the seawater system. This due to the risk of sea water or water from the central
cooling system entering the vessel.
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Draining the seawater system

Keep the engine room heated or use an antifreeze
coolant in the seawater system. Otherwise the sea-
water system must be drained when there is a risk of
freezing in cold weather.
1. Close the seawater in- and outlet cocks.
2. Drain the coolant from the external cooling sys-
tem.
IMPORTANT! Check that the coolant really
drains. Deposits may need to be removed from
inside the drain plugs/taps.

Check and Change the zinc anodes

1. Drain the external cooling water as described in
the chapter draining the seawater system.
2. Unscrew the zinc anodes from the heat exchan-
ger.
3. Change the anode if less than 50% remains. If
not, clean the anode with emery cloth to remove
the layer of oxide.
IMPORTANT! Do not use a wire brush or other
metal tool for cleaning as this may decrease the
galvanic protection.
4. Fit the zinc anodes. Make sure there is good con-
tact between the anode and the metal goods.
5. Open the seawater cocks before starting the eng-
ine
6. Check the installation and make sure there are no
leaks.

Seawater filter check/change

If the vessel is equipped with a seawater filter refer to
the maintenance description supplied by the supplier
of the filter.
NOTE! If the water wherein the vessel operates is se-
verely polluted, contains large amounts of seaweed,
etc., the filter must be checked more often than is
specified. The filter can otherwise become clogged
and the engine overheated.