Humminbird PiranhaMAX 155 Installation And Operation Manual page 61

5. The unit comes on before I press the POWER-MENU key, and won't
turn off.
Check the transducer cable — if the outer jacket of the cable has been cut
and the cable is in contact with bare metal, you will need to repair the cut with
electrical tape. If there is no problem with the cable, disconnect the transducer
from the unit and see if the problem is corrected, to confirm the source of the
problem.
6. I get gaps in the reading at high speeds.
Your transducer needs adjusting. If the transducer is transom-mounted, there
are two adjustments available to you: height and running angle. Make small
adjustments and run the boat at high speeds to determine the effect. It may
take several tries to optimize high-speed operation. This can also be a result of
air or turbulence in the transducer location caused by rivets, ribs, etc.
7. My unit loses power at high speeds.
Your PiranhaMAX has over-voltage protection that turns the unit off when input
voltage exceeds 20 VDC. Some outboard motors do not effectively regulate the
power output of the engine's alternator and can produce voltage in excess of
20 Volts when running at high RPMs.
8. The display begins to fade out. Images are not as sharp as normal.
Check the input voltage. The PiranhaMAX will not operate on input voltages
below 10 VDC.
9. The display shows many black dots at high speeds and high
sensitivity settings.
You are seeing noise or interference caused by one of several sources. Noise
can be caused by electronic devices. Turn off any nearby electronics and see
if the problem goes away. Noise can also be caused by the engine. If engine
noise is causing the interference, the problem will intensify at higher RPMs.
Increase the engine speed with the boat stationary to isolate this cause.
Propeller cavitation can also appear as noise on the display. If the transducer
is mounted too close to the propeller, the turbulence generated can interfere
with the sonar signal. Make sure that the transducer is mounted at least 15"
(380 mm) from the propeller.
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Troubleshooting