Furuno DFF-3D Operator'S Manual Download

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APPENDIX 4 INSTALLATION OF TRANSDUCER TM54

AP-10

Mounting & Adjusting the Bracket

CAUTION

: Do not position the leading edge of the transducer

lower than the trailing edge because aeration will occur.

CAUTION:

Do not position the transducer deeper in the water

than necessary to avoid increasing drag, spray, and water noise
and reducing boat speed.

CAUTION

: The stainless steel bracket must be isolated from a

metal hull to prevent electrolytic corrosion. If no shim is being
used, place non-metal insulating washers between the bracket
and the metal hull.

1. Apply marine sealant to the threads of four of the hex-washer-

head screws to prevent water seepage into the transom. Being
sure any shim(s) is in place, screw the bracket to the hull using
a socket wrench (see Figure 4). Do not tighten the screws at this
time.

2. Reinstall the transducer. While holding the transducer assembly

against the bracket, insert the hinge pin through the upper hole
in the bracket and the support. Slide the spacer onto the pin
and push it through the remaining hole in the support and the
bracket. Reattach the safety ring.

3. Slide a washer onto the locking pin. Push it through the lower

hole in the bracket, slide it along the channel in the support, and
through the second hole in the bracket. Slide the second
washer onto the free end of the pin and reattach the safety ring.

4. With the transducer in the operational position, Use a straight edge

to sight the underside of the transducer relative to the underside of
the hull (see Figure 5). The trailing edge of the transducer should
be 1–6mm (1/16 –1/4") below the leading edge.

5. Using the vertical adjustment space in the bracket slots, slide the

assembly up or down until the bottom inside corner of the
transducer projections 0–3mm (0–1/8") below the bottom of the
hull (see Figure 1). When you are satisfied with the position of the
transducer, tighten the four bracket screws. For clear access to
the screws, remove the transducer assembly from the bracket
(see Figure 4). When reattaching, be sure to include the spacer.

Testing on the Water

1. Test the transducer at 165kHz with the engine off.

2. Become familiar with your echosounder’s performance at a

speed of 4kn (5 MPH).

3. Gradually increase the boat speed and observe the gradual

decline of performance due to turbulent water flowing under the
transducer’s face.

NOTE

: As the speed increases the performance at 50kHz will

deteriorate more rapidly because more acoustic noise is
generated at low frequencies.

4. If the decline in performance is sudden (not gradual), identify

the boat speed at which the onset occurred. Return the boat to
this speed, then gradually increase speed while making
moderate turns in both directions.

5. If the performance improves while turning to the side on which the

transducer is installed, it’s position probably needs adjustment.
The transducer is probably in turbulent or aerated water.

To improve performance, try the following, one at a time,
in the order given .
a. Increase the transducer’s angle in the water. Review

“Compensating for Transom Angle: Shims” and see Figure 5.

b. Move the transducer deeper into the water in increments of

3mm (1/8") (see Figure 1).

c. Move the transducer closer to the centerline of the boat.

Fill unused screw holes with marine sealant.

6. Calibration —To match the speed shown on the display to the

actual speed of the boat, you may need to calibrate the
instrument. Refer to your instrument owner’s manual.

Stabilizing the Bracket

1. Prevent the bracket from moving out of position using the

remaining hex-washer-head screw. Drill the hole for the
stabilizing screw through the center hole of the bracket, any
shim(s), and the hull (see Figure 6).

12° transom angle

13° transom angle

Figure 5. Adjusting the transducer angle

21° transom angle

9° transom angle

parallel

slight angle

one

shim

three shims

taper down

slight angle