Humminbird GR16 - Manual (Page 52)

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 pro-
portionately; 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.
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