The downrigger cable maintains a
fish-attracting positive electric
potential because the Black Box
draws electrons from the downrigger
line faster than electrons are donated
through the water from boat metals.
D.C.Reid, BC Outdoors Sport Fishing, June-
August 2002.
The charge from the zinc to the downrigger line runs
negative to positive because stainless steel attracts
and sheds electrons faster than water can transmit them
from the boat's zinc. This creates a relative absence of
electrons, or relative positive charge around the downrigger
line. A sleeve over the downrigger wire is connected to a wire
which runs to the Black Box. By altering the rate at which electrons
are transmitted from the surface of the downrigger line to the Box, the
Black Box modifies the charge around the entire length of the cable. The circuit
is completed as electricity is attracted by the positive or red battery terminal,
passes through the battery to the negative post whereupon one lead powers the
black box and the other connects through the bonding wire to the engine or
outdrive. At this point, the circle begins again with the electrons being attracted
back toward the downrigger line.
The Black Box is most effective when connected to all the downriggers on the
boat, providing a uniform positive charge around the hull. Up to 6 downriggers
can be connected to one Black Box. A short drop back leader length is
recommended in order to keep the lure within the electric field. Longer drop back
leader lengths tend to put the lure into the weaker part of the field. Leaders of
10-20 feet work well. Depth can also alter the effectiveness of the Black Box.
You may need to increase the charge slightly on your Black Box to compensate
for deeper fishing (100' or more). Do not forget to turn it back down when fishing
nearer the surface. The Black Box is also very effective when drift fishing, as fish
have longer to react to the positive voltage effect and it can attract fish from as
much as 300 feet away. The Black Box has also been used successfully for ice
fishing. A Black Box is effective on all types of boat hull, provided it is properly
bonded and equipped with zinc anodes. Aluminum hulls actually act as the
negative side of the electrolysis circuit, creating a wider electric field and
attracting fish from a broader area. Some vessels may be so well bonded that
the natural electrolysis is ideal. These boats may not benefit from the use of a
Black Box. A Black Box draws very little power (about .1 amp at full load). It has
no effect on other electronics on board.
Natural Electrolysis
"Natural" electrolysis occurs on most boats even without a Black Box. There are
several factors which will affect your boat's electrical condition. Your downrigger
spool and wire line should be insulated from the boat hull in order to allow natural
electrolysis to occur. All models of Scotty downriggers are fully insulated.· The
sacrificial zinc anodes on your boat should not be more than 50% dissolved.
They should be clean and unpainted. If you trailer your boat often, you should
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