Humminbird 365i manual Finding the Cause of Noise

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 RP Ms while
	the boat is in n eutral and stat ionary to see if
	the n oise i ncreases pr oportionately; if noi se
	appears w hen you r ev the e			ngine, the
	problem could be the spark plugs, a lternator,
	or tachometer wiring. Replace the spark plugs
	with re sistor plugs, install a n alternator filter,
	or route th	e c ontrol he	ad	power a nd
	transducer	cables aw ay	from	the e ngine
	wiring.

Cavitation from the boat’s propeller

Turbulence created by the pr opeller can cause noise; m ake sure t he tr ansducer i s mo unted at least 15” (38 cm) from the propeller, and that the water flows smoothly over the face of the transducer at all times.

Troubleshooting 106