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4. The boat must be
moving
at
aslowtrolling speed
toseefish arches. If the boat
is
motionless,
fish
stay
in the
cone,
showing
on the
display
as
straight
horizontal
lines.
ELECTRICAL NOISE
A
major
cause of sonar
problems
is
electrical noise. This
usually
appears
on the
sonar's
display
as random
patterns
of dots or
lines. In severe
cases,
it can
completely
cover the screen with black
dots,
or cause the unit
operate erraticly,
or not at all.
To
eliminate or minimize the effects of electrical
noise,
first
try
to determine the
cause, With the boat at rest in the
water,
the
first
thing you
should do is turn all
electrical
equipment
on the boat off. Make certain the
engine
is
off,
also. Turn
on the sonar
unit,
then turn ASP off. There should be a
steady
bottom
signal
on
the
display.
Nowturn on
each
piece
of electrical
equipment
on the boat and view
the effect on the sonar's
display.
For
example,
turn on the
bilge pump
and view
the sonar
display
for noise. If no noise is
present,
turn the
pump
off,
then turn
on the VHF radio and
transmit.
Keep doing
this until all electrical
equipment
has
been turned
on,
their
effect on the sonar
display
noted,
then turned off.
If
you
find noise interference
from an electrical
instrument,
trolling
motor,
pump.
or
radio,
try
to isolate the
problem.
You can
usually
re-route the sonar unit's
power
cable and transducer cable
away
from the
wiring
that is
causing
the
interference. VHF radio antenna
cables radiate noise when
transmitting,
so be
certain to
keep
the sonar's wires
awayfrom
it. You
may
need to route the sonar
unit's
powercable directlyto
the
batteryto
isolate it from
otherwiring
on the boat.
If no noise
displays
on the sonar unit from
electrical
equipment,
then make
certain
everything except
the sonar
unit Is turned
off,
then start the
engine.
Increase the RPM with the
gearshift
in neutral. If
noise
appears
on the
display,
the
problem
could be one of three
things;
spark plugs,
alternator,
ortachometer
wiring.
Try using resistorspark plugs, alternatorfilters,
or
routing
the sonarunit's
power
cable
away
from
engine wiring. Again, routing
the
powercable directly
to
the
battery
helps
eliminate noise
problems.
Make certain to use the in-line fuse
supplied
with the unit when
wiring
the
power
cable to the
battery.
When no noise
appears
on the sonar unit after all of the
above
tests,
then the
noise source Is
probably
cavitation.
Many
novices or
persons
with limited
experience
make
hasty
sonar installations which
function
perfectly
in shallow
water,
orwhen the boat is at rest. In
nearly
all
cases,
the cause of
the malfunction
will be the location and/or
angle
of the
transducer. The face of the transducer
must be
placed
in a location that has a
smooth flow of water at all boat
speeds.
Read
your
transducer owners
manual for the best
mounting position.
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