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71
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
The boat’s engine
Cavitation from the boat’s
propeller
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.
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.
Turbulence created by the propeller can cause noise;
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.
70
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 at
high speeds.
When the boat moves at higher
speeds, the bottom disappears
or suddenly weakens, or the
display contains gaps.
There are no fish detected, even
when you know they are in the
water under the boat, or sonar
readings seem weak or faulty.
If the power output of your boat’s engine is unregulated,
the control head may be protecting itself using its over-
voltage protection feature. Make sure the input voltage
does not exceed 20 Volts.
The transducer position may need to be adjusted. A mix
of air and water flowing around the transducer
(cavitation) may be interfering with the interpretation of
sonar data. See your Installation Guide for 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.
Sonar readings may be affected if the transducer is not
positioned correctly (i.e. mounted at an angle, not
straight down), or there is some kind of mechanical
interference, either because it is mounted inside a hull
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 boats engine may be interfering
with sonar reception. See Finding the Cause of Noise for
more information.
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