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Bottom echo disappears at high speeds or erratic digital
reading or weak bottom echo while boat is moving
1. The transducer may be in turbulent water. It must be mounted in a
smooth flow of water for the sonar to work at all boat speeds.
2. Electrical noise from the boat's motor can interfere with the sonar.
This causes the sonar to automatically increase the noise rejection level.
This can cause the unit to eliminate weaker signals (fish) from the
display. Try using resistor spark plugs or routing the sonar unit's power
and transducer cables away from other electrical wiring on the boat.
No fish arches when the Fish I.D. feature is off:
1. Make certain the transducer is pointing straight down. This is the
most common problem if a partial arch is displayed.
2. The sensitivity may not be high enough. If the sensitivity is not high
enough, the unit shows the fish only when it is in the center of the cone.
3. Use the Zoom feature. It is much easier to display fish arches when
zoomed in on a small range of water than a large one. 4. The boat must
be moving at a slow trolling speed to see fish arches. If the boat is
motionless, fish are displayed as straight horizontal lines.
NOISE
Noise usually appears on the sonar's display as random patterns of dots
or lines. In severe cases, it can completely cover the screen with black
dots, or cause the unit to operate erratically, or not at all.
To eliminate or minimize the effects of electrical noise, try to determine
the cause. With the boat at rest in the water, turn all electrical
equipment on the boat off. Make sure the engine is also off. Turn on
your sonar, then turn off Noise Reject {ASP feature (Advanced Signal
Processing)]. Sensitivity should be set at 90-95 percent. There should be
a steady bottom signal on the display. Now turn on each piece of
electrical equipment on the boat and view the effect on the sonar's
display. If you find noise interference from an electrical instrument,
trolling motor, pump, or radio, try to isolate the problem. You can usually
reroute the sonar unit's power cable and transducer cable away from the
wiring that is causing the interference.
If no noise displays on the sonar unit from electrical equipment, start
the engine and increase the RPM with the gearshift in neutral. If noise
appears on the display, the problem could be one of three things; spark
plugs, alternator, or tachometer wiring. Try using resistor spark plugs,
alternator filters, or routing the sonar unit's power cable away from
engine wiring. When no noise appears on the sonar unit after all of the
above tests, then the noise source is probably cavitation.