NorthStar EXPLORER 650 Installation And Operation Manual page 84

i Electrical noise from the boat's engine or
an accessory may be interfering with the
transducer(s) and/or the Explorer. This may
cause the Explorer to automatically decrease
the Gain unless using Manual Gain.
The Explorer thus eliminates weaker signals
such as fish or even the bottom from the
display. This may be checked by switching
off other instruments, accessories (e.g. bilge
pump) and the motor until the offending
device is located. To stop problems from
electrical noise, try:
- re-routing the power and transducer
cable(s) away from the boat's other
electrical wiring.
- routing the display unit's power cable
directly to the battery with an in-line fuse.
4-2 Bottom is not displayed:
a The Explorer may have Manual Range
selected and the depth may be outside the
range value selected. Either change the
Explorer to Auto Range or select another
depth range (see section 8-5).
b The depth may be outside the Explorer's
range. While in Auto Range, the display unit will
display "--.-" to indicate that there is no bottom
detected. A display of the bottom should
reappear when in shallower water.
4-3 The bottom is displayed too far up
the screen:
The Explorer may have Manual Range
selected and the selected Range value is
too high for the depth. Either change the
Explorer to Auto Range or select another
depth range (see section 8-5)
84
4-4 Bottom echo disappears or erratic digital
a
b
c
4-5 There is a double bottom trace displayed:
a
b
c
Northstar Explorer 650 Installation and Operation Manual
reading while the boat is moving:
Ensure the back of the bottom surface of
the transducer is slightly lower than the
front and the front is as deep in the water as
possible in order to minimise the generation
of bubbles through cavitation. (See the
Transom Transducers Installation Guide, for
more information.)
The transducer may be in turbulent water.
Air bubbles in the water disrupt the echoes
returned, interfering with the Explorer's
ability to find the bottom or other targets.
This often happens when the boat is
reversed. The transducer must be mounted
in a smooth flow of water in order for the
Explorer to work at all boat speeds.
Electrical noise from the boat's motor
can interfere with the Explorer. Try some
suppression spark plugs.
The boat may be in an area that generates
shadows (see section 8-2).
In shallow water, the echoes may bounce.
Reduce the gain setting (see section 8-6)
and/or reduce the sonar pulse power (see
section 17-3).
Decrease the Range.