Fish Finders - Finding The Cause of Noise

[GLF]

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

Other electronic devices

How to isolate it

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 reappears.

Possible source of noise

The boats engine

How to isolate it

To determine whether the boats 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 the 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 engine wiring.

Possible source of noise

Cavitation from the boats propeller(s)

How to isolate it

Turbulence created by the propeller can cause noise. make sure the transducer is mounted at least 15" from the propeller, and that the water flows smoothly over the face of the transducer at all times.

[GLF]

One thing you can also do is to turn the boat motor off and see if the noise goes away.