Airmar TM256 Owner'S Manual & Installation Instructions Download Page 4

 

4. Position the second cable clamp halfway between the first 

clamp and the cable hole. Mark this mounting hole.

5. If a hole has been drilled through the transom, open the large 

slot in the transom cable cover. Position the cover over the 
cable where it enters the hull. Mark the two mounting holes.

6. At each of the marked locations, use a 3mm or 1/8" bit to drill a 

hole 10mm (3/8") deep. To prevent drilling too deeply, wrap 
masking tape around the bit 10mm (3/8") from the point.

7. Allow about 10cm (4") of slack in the cable below the lower cable 

clamp to accommodate the sensor in the “released” position.

8. Apply marine sealant to the threads of the #6 x 1/2" self-tapping 

screw to prevent water from seeping into the transom.If you 
have drilled a hole through the transom, apply marine sealant to 
the space around the cable where it passes through the 
transom. 

9. Position the two cable clamps over the cable and fasten them in 

place. If used, push the cable cover over the cable and screw it 
in place.

10.Route the cable to the instrument 

 

being careful

 

 not to tear the 

cable jacket when passing it through the bulkhead(s) and other 
parts of the boat. To reduce electrical interference, separate the 
sensor cable from other electrical wiring and the engine(s). Coil 
any excess cable and secure it in place with zip-ties to prevent 
damage.

11.Refer to your echosounder owner’s manual to connect the 

transducer to the instrument.

 

Checking for Leaks

 

Warning

 

: When the boat is placed in the water, 

 

immediately

 

 

check for leaks around the screws and any hole drilled in the hull. 
Never install a sensor and leave the boat in the water unchecked 
for several days.

 

Anti-fouling Paint

 

Marine growth can accumulate rapidly on the transducer’s surface 
reducing performance within weeks. Surfaces exposed to salt 
water 

 

must

 

 be coated with anti-fouling paint.Use 

 

water based

 

 

anti-fouling paint only. 

 

Never 

 

use ketone based paint, since 

ketones can attack many types of plastic possibly damaging the 
transducer.

Apply paint to the transducer and all parts of the bracket up to 
100mm (4") 

 

above the waterline

 

. Repaint every 6 months or at the 

beginning of each boating season. 

 

Operation

 

“Up” position

 

Store the transducer in the “up” position when it is not in use (see 
Figure 2). In the “up” position, the transducer is protected from 
impact, but note that 

 

the bracket will not release

 

. The “up” 

position must be used when running at high speed [above 30kn 
(35MPH)] to minimize drag. The “up” position will provide very 
good fishfinding at boat speeds below 6kn (7MPH). Raise the 
transducer to the “up” position by pulling on the latch line to 
release the latch while pulling on the hoist line to raise the support 
tube until the latch engages the lower latch pin (see Figure 4).

 

“Down” Position

 

Place the transducer in the “down” position for normal operation. 
The bracket will release in this position. To lower the transducer, 
pull on the latch line and lower the support tube. 

 

Be sure

 

 that the 

latch re-engages with the upper latch pin (see Figure 4).

 

“Released” Position

 

When the transducer is in the “down” position and hits an object in 
the water, the bracket will release (see Figure 2). Also, when the 
boat is making headway, the water exerts drag on the transducer. 
As the boat speed increases, the force on the bracket increases 
dramatically. Depending on the water conditions and the amount 
the transducer projects below the transom, the transducer bracket 
will release at about 40kn (46MPH).

After release, the transducer will ride atop the outwash from the 
transom and cause minimal drag while the boat is making 
headway. The transducer can survive in this condition if the water 
is calm. However, pitching and rolling in rough water will stress the 
bracket. Also, the transducer will sink at zero boat speed. 

 

The 

release feature is not intended to be a substitute for hoisting 
the transducer

 

.

 

Caution

 

: Always reset the transducer in the “down” position as 

soon as possible using a blunt pole.

 

Maintenance and Parts

 

Removing the Transducer

 

1. Lower the transducer into the “down” position.

2. Separate the transducer assembly from the mounting plate by 

removing one safety ring and withdrawing the hinge pin (see 
Figure 4).

3. Remove the bracket by grasping the support tube near the 

mounting shoe and pulling away from the boat.

4. Replace the hinge pin and safety ring on the bracket.

 

Cleaning 

 

Keep the support tube, guides, and rollers free of sand and grit by 
washing them with mild household detergent. 

 

Do not

 

 use a 

lubricant, since grit will stick to it increasing friction and wear.

If fouling is severe, use a stiff brush or putty knife to remove the 
growth, 

 

being careful

 

 to avoid making scratches on the 

transducer’s face. Wet sanding the fouled surfaces with #220 or 
finer grade wet/dry paper is permissible.

 

Storage

 

Avoid extremes of temperature. Low temperatures make plastic 
brittle, and although the transducer is designed to withstand 
temperatures up to 70

 

°

 

C (160

 

°

 

F), it is best to store the transducer 

at a moderate temperature.

 

Parts

 

Lost, broken, and warn parts should be replaced immediately and 
can be obtained from your marine dealer or instrument 
manufacturer:

Bracket Assembly

33-432-01

 

Transducer Replacement

 

The information needed to order a replacement transducer is 
printed on the cable tag. 

 

Do not

 

 remove this tag. When ordering, 

specify the part number, date, and frequency in kHz. For 
convenient reference, record this information where indicated 
near the top of page one.

 

AIRMAR

 

TECHNOLOGY CORPORATION

35 Meadowbrook Drive, Milford, New Hampshire 03055-4613, USA 

 

                                                                                                 ■

 

 www.airmar.com 

 

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