Do not paint the external ground plate with bottom paint as this
prevents the plate from grounding out with the seawater.
Periodically inspect the connections in the bilge to see that they are
tight and clean and free from corrosion.
ELECTROLYSIS AND CORROSION
Underwater corrosion results from an electrical current passing between
dissimilar metals in water. The electrical current develops from the
difference in relative potentials or voltages of the metals in sea
water. The least similar metals are in potential, the more galvanic
corrosion occurs. For this reason, Cape Dory uses fittings below the
waterline with the most similar potential in the galvanic series and
bond each fitting together with an external ground plate.
A sacrificial zinc anode is provided on the propeller shaft of each
boat. It is called a Perry Nut and its purpose is to reduce galvanic
corrosion of the underwater fittings by sacrificing itself and being
eaten away rather than the other fittings.
With stray current corrosion, you will find similar corrosion of
external parts. However, this corrosion is caused when a direct current
from a battery or other source makes contact through sea water with
metal parts and is usually more severe in results. A zinc anode will
lessen the effect of this but not correct it. Check and maintain wire
connections on switches and thru hulls to keep equipment in normal
working order to insure against electrolysis or other problems
developing. Stray current corrosion can be stopped immediately by
disconnecting the batteries and the shore power from the boat's
electrical system.
Electrolysis can occur from sources other than one's own boat.
Depending on the composition and characteristic of the local waters, it
will either be minimized or enhanced by electrical leaks from faulty
shore power installations, misused battery chargers, or currents
generated from adjacent boats.
Maintain a close check of underwater fittings to correct any problems
early should they occur.
IX. FRESH WATER SYSTEM
The Cape Dory 270 has a 46 gallon polypropylene tank located on the port
side under the settee. The water fill plate is located outboard along
the port side deck adjacent to the head. When filling the tank it is
best to have someone stationed below to observe the tank filling up.
The inspection plates on top can be removed to monitor the water level
in the tanks to avoid over flow through the vent line into the hanging
locker in the head. A vent line runs up inside the wet locker to the
underside of the deck. The pick up tube extends into the forward end of
the tank and runs back under the port berth top to the galley. Access
to al1 tank fittings may be gained through holes cut in the top of the
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