Airmar 1 kW—TM258 - Manual (Page 2)

Figure 2. Stepped transom space requirement
TM258: 244mm (9-3/4")
Boat Types
• Single drive—Mount a minimum of 15cm (6") beyond the
swing radius of the propeller (see Figure 1).
• Twin drive—Mount between the drives a minimum of 15cm
(6") beyond the swing radius of the propeller.
• Trim tabs—Mount inside the trim tab, space permitting.
• Stepped transom—Mount the transducer on the lowest step
being sure there is enough space above the bracket for it to
release and rotate the transducer upward (see Figure 2).
Installation
Assembling the Transducer & Bracket
1. Thread the cable through the large hole in the transducer
support (see Figure 3).
2. Fasten the support to the transducer using the three socket-
head-cap screws and washers supplied. Tighten the screws
with the 3/16" Allen wrench supplied.
3. Attach a safety ring to one end of each pin (see Figure 4).
4. While holding the transducer assembly against the bracket, insert
a 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. Attach a second safety ring.
This pin will function as a hinge when the transducer is released.
5. Slide a washer onto the remaining 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 attach the
second safety ring. This will function as the locking pin to hold
the transducer in the operational position when underway.
Compensating for Transom Angle: Shims
For the best performance, the transducer beam must be aimed
straight at the bottom. Since the transom of most boats is angled,
the bracket must compensate for it. Measure the transom angle of
the boat with an angle finder.
• Standard transom (12° transom angle)—The bracket is
designed for a standard 12° transom angle. No shim is needed
for this installation. If your boat is capable of speeds above
20kn (28MPH), install the bracket with one 3° shim, taper
down. This will ensure that the transducer is in contact with the
water at high speeds.
• Using shims—The bracket is supplied with three shims; each
one has a 3° angle. Up to three shims can be combined for a
maximum of 9°. The shims are designed to mate together. Two
bosses on the face fit into recesses in the back of another shim or
the holes in the bracket.
- Transom angles greater than 12°—Add the appropriate
number of shims with the taper up to the 12° bracket angle.
- Transom angles less than 12°—To reduce the bracket’s
12° angle, group the appropriate number of shims with the
taper down.
• If you are unsure about using the shim(s), experiment with
the them by following the instructions “Mounting & Adjusting the
Bracket.”
Hole Drilling
CAUTION: To prevent drilling too deeply, wrap masking tape
around the bit 22mm (7/8") from the point.
NOTE: Fiberglass hull—Minimize surface cracking by running the
drill in reverse until the gelcoat is penetrated.
1. At the selected mounting location, position the assembly so the
transducer projects 3mm (1/8") below the bottom edge of the
transom (see Figure 1). Be sure any shim(s) is in place. (You
may want to tape the shim(s) to the bracket temporarily.) With
the transducer in the operational position, mark the bottom
corners of the bracket.
2. Remove the transducer assembly from the bracket by removing
the locking pin and the hinge pin (see Figure 4). Hold the
bracket with any shim(s) in place against the transom at the
marked location. Draw an “X” at 12mm (1/2") from the top and
the bottom of each slot (see Figure 6).
3. Using a 5mm, #4, or 7/32" drill bit, drill four holes 22mm (7/8")
deep at the marked locations.
2
Figure 3. Assembling the transducer
Copyright © 2009 Airmar Technology Corp.
Copyright © 2009 - 2014 Airmar Technology Corp.
TM260, TM265, TM275LH-W: 260mm (10-1/4")
TM270W: 260mm (10-1/4")
bracket
support
transducer
hinge
locking
spacer
safety
Copyright © 2009 Airmar Technology Corp.
Figure 4. Attaching the transducer to the bracket
screw (3)
washer (3)
support
transducer
cable
washer (2)
pin
pin
ring (4)
detail
channel