Installation Manual

Chapter 6 N38143
Page 40
As many of the connections may be splashed with sea water they should be soldered wherever possible and
clamped elsewhere, with the joint protected from corrosion by neoprene paint, or a similar material, to exclude
water.
Bonding of aluminium boats is a special case as the various appliances on board should be earth free and
therefore to avoid stray currents all appliances must be earthed to a single terminal.
Grounding is required for safety if voltages are high, i.e. when there is a 240 volt generator on board or when a
shore line is connected. Grounding (or earthing) must not be confused with the term ‘earth return’. Earth return
carries current, whereas grounding (earthing) does not.
Another source of unplanned current giving raise to a form of stray current corrosion is an earth connection
from a shore line. When a shore line is in use the boat system should be protected from earth leakage by an
earth leakage switch on shore but as additional safety there should be a switch on board the boat.
Caution: This section on bonding covers a typical system and has been included for guidance purposes only.
It may not be appropriate for your boat. As installations vary, it is advised that specic recommendations from
a specialist in the subject of electrolytic corrosion are obtained.
Zinc Anode bonding system
(a) Electrolytic corrosion within the engine cooling system and transmission can be much reduced or eliminated
by bonding the engine to a Zinc anode which is used to protect through the hull metal ttings and other metal
components that are in contact with sea water. The engine is tted with a stud that may be used for this
purpose. The stud is identied by a label, (B) shown below:
Battery and starter cables
(a) Batteries
There are two standards by which battery performance is commonly stated:-
BS3911 uses the current which can be maintained for 60 seconds, without the voltage of a nominal 12V
battery dropping below 8.4 volts, whilst at a temperature of -18oC.
SAE J537 is similar except that the current is only maintained for 30 seconds and the voltage is allowed to
fall to 7.2 volts.
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