Corrosion Information - Volvo Penta AD31L Instruction Book

Electrolytic corrosion
Your boat and its engine/transmission package are
equipped with sacrificial zinc anodes (replace with
magnesium anodes in freshwater lakes) in order to
protect the drive and propellers against galvanic
corrosion. This protection can malfunction if so-cal-
led leakage currents from the electrical system oc-
cur. This can happen if faulty equipment is used or
the connection of electrical equipment to the negati-
ve pole is incorrect (grounding, protector ground).
The following should always be observed:
The main switch for the engine should be connected
to the positive (+) pole of the battery. The main
switch should disconnect all circuits. Electrical ca-
bles should be routed and clamped so that they are
not exposed to dampness or the risk of exposure to
any bilge water in the keelson.
If several batteries are used, there should be sepa-
rate switches for extra equipment. There should
also be a main switch between the positive (+) pole
of the extra battery and the fuse panel for the boat's
electrical equipment. The main switch for the extra
battery should disconnect all circuits connected to it
and should be switched off when there is no longer
a need for electricity. The main switch for the engi-
ne should be disconnected as soon as the engine is
stopped.
The engine or drive must not be electrically connec-
ted with other equipment such as trim tabs, ladders,
etc. The engine and drive must not be used as gro-
und for radio or navigation equipment or for other
electrical equipment where separate ground cables
are used. All such separate ground connections
should be gathered to a common ground point sepa-
rated from the engine/drive.
If shore power is connected, no protector ground
must be connected to the engine or to any other
ground point in the boat.
The transformer for shore power should have the
protector ground on the input side (120/220 V) and
the negative connection on the output side (12/24
V) without any connection to each other.
WARNING! Electrolytic corrosion resulting
from leakage currents may cause severe and
expensive damage to the boat's equipment in
a short space of time. Work on the boat's
low-tension circuit must only be carried out
by trained electricians or by people who have
expertise in the subject. Installation or work
on the shore power equipment must only be
carried out by electricians qualified to work
on high-voltage installations.
30
Galvanic corrosion
Your drive has been protected from galvanic corro-
sion in various ways. Apart from sacrificial anodes,
there are grounding loops that provide a link bet-
ween the various separate parts of the drive. Check
annually that loops are intact and ensure good con-
tact. A broken connection can result in considerable
corrosion of an individual component despite func-
tioning protection for the rest of the drive.
Volvo Penta drives are equipped as standard with
sacrificial anodesintended for salt water. These are
furthermore dimensioned for the propellers with
which the drive is equipped as standard. For DP
drive the following must be borne in mind regarding
freshwater operation and propeller replacement.
Boats that are operated primarily in fresh water
should have these anodes replaced by a magnesi-
um ring, VP Part No. 876138-9. DP drives fitted
with stainless steel propellers should be provided
with two zinc plates on the shield. These are fitted
with 2 bolts Part No. 963701-8 and 2 spacer
sleeves 854486-8.
Anti-fouling bottom paints or incorrectly undertaken
painting can increase galvanic corrosion. Also refer
to page 33 regarding bottom painting.