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531427-1_C - 767_Man_Eng.qxd
10/25/2005
Display Problems
There are several main conditions or sources of possible interference that may cause problems
with the quality of the information displayed on the control head. Look in the following table for
some symptoms of display problems and possible solutions:
Problem
Possible Cause
The control head loses power
If the power output of your boat's engine is
at high speeds.
unregulated, the control head may be protecting itself
using its over-voltage protection feature. Make sure the
input voltage does not exceed 20 Volts.
When the boat moves at
The transducer position may need to be adjusted. A
higher speeds, the bottom
mix of air and water flowing around the transducer
disappears or suddenly
(cavitation) may be interfering with the interpretation
weakens, or the display
of sonar data. See your Installation Guide for
contains gaps.
suggestions on adjusting the transducer position.
Electrical noise from the boat's engine may be
interfering with sonar reception. See Finding the Cause
of Noise for more information.
There are no fish detected,
Sonar readings may be affected if the transducer is not
even when you know they are
positioned correctly (i.e. mounted at an angle, not
in the water under the boat,
straight down), or there is some kind of mechanical
or sonar readings seem weak
interference, either because it is mounted inside a hull
or faulty.
that is too thick for proper sonar transmission, the bond
between the transducer and the hull is not airtight, or
because the transducer is dirty. Check with your
Installation Guide for guidance on re-positioning the
transducer, and make sure the transducer is clean.
Low battery voltage may be affecting the power of
signal transmission.
Electrical noise from the boat's engine may be
interfering with sonar reception. See Finding the Cause
of Noise for more information.
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Finding the Cause of Noise
Electrical noise usually affects the display with many black dots at high speeds, and high
sensitivity readings. One or more of the following sources can cause noise or interference:
Possible Source of Noise
Isolation
Other electronic devices
Turn off any nearby electronic devices to see if the
problem goes away, then turn them on one at a time to
see if the noise re-appears.
The boat's engine
To determine whether the boat's engine is the source
of the noise, increase the RPMs while the boat is in
neutral and stationary to see if the noise increases
proportionately; if noise appears when you rev the
engine, the problem could be the spark plugs, alternator,
or tachometer wiring. Replace the spark plugs with
resistor plugs, install an alternator filter, or route the
control head power and transducer cables away from the
engine wiring.
Cavitation from the boat's
Turbulence created by the propeller can cause noise;
propeller
make sure the transducer is mounted at least 15" (38 cm)
from the propeller, and that the water flows smoothly
over the face of the transducer at all times.
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