Humminbird 727, 717 manual Display Problems, Possible Cause, does not exceed 20 Volts

531524-1_A - 717 & 727 Man_Eng.qxp 9/30/2006 7:24 PM Page 79

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 If the power output of your boat’s engine is unregulated, power at high speeds. 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 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.

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 boat’s engine may be interfering with sonar reception. See Finding the Cause of Noise for more information.

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