Humminbird ] 981 - Manual (Page 21)

To adjust the running position of the transducer:
The transducer mounting bracket allows height and tilt adjustment, while the pivot
bolt allows angular adjustment. These adjustments will help reduce cavitation.
Initially, adjust the transducer as described in the following paragraphs. Further
adjustment may be necessary to refine the installation after high-speed testing.
1. First, adjust the pivot angle of the transducer body, so it is parallel with the
length of the hull of the boat.
2. Fully tighten the two pivot screws, using the supplied Allen wrench. Access to
the pivot screws is provided by the lower holes in the side of the mounting
bracket. It may be necessary to re-tighten the pivot bolt after initial use as the
plastic may still be conforming to the pressure from the lock washers.
3. Adjust the height of the assembly so the face of the
transducer is 1/8" (3 mm) to 1/4" (6 mm) beneath the
bottom of the transom, and fully tighten the three
mounting screws.
4. In order to gain access to the mounting screws, the
transducer assembly must be pivoted up in the bracket as
shown. Be careful not to alter the running angle as some
force is necessary to pivot the assembly.
5. If access to the top mounting hole is not possible due to the selected height of
the transducer, fully tighten the two lower screws, then simply remove the
headed pivot pin and the transducer assembly, and tighten the top screw, then
reassemble.
6. Confirm that the pivot angle has not changed and that all mounting screws are
fully tightened.
To route the transom transducer cable:
The transducer cable has a low profile connector that must be routed to the point
where the control head is mounted. There are several ways to route the transducer
cable to the area where the control head will be installed. The most common
procedure routes the cable through the transom into the boat.
NOTE: Your transducer may not look exactly like the transducer shown in the illustrations,
but it will mount in exactly the same way.
NOTE: Your boat may have a pre-existing wiring channel or conduit that you can use for the
transducer cable.
1. Unplug the other end of the transducer cable from the control head. Make sure
that the cable is long enough to accommodate the planned route by running
the cable over the transom.
CAUTION! Do not cut or shorten the transducer cable, and try not to damage the cable
insulation. Route the cable as far as possible from any VHF radio antenna cables or
tachometer cables to reduce the possibility of interference. If the cable is too short, extension
cables are available to extend the transducer cable up to a total of 50' (15 m). For assistance,
contact the Customer Resource Center at www.humminbird.com or call 1-800-633-1468 for
more information.
NOTE: Since the transducer may need to pivot up to 90° in the bracket if it strikes an object,
make sure there is sufficient cable slack to accommodate this motion. It is best to route the
cable to the side of the transducer so the cable will not be damaged by the rotation of the
transducer. Tighten the Mounting Screws
Normal Cavitation Cavitation that will cause
erratic sonar readings
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