Airmar P48W - Manual (Page 2)

allow 76mm
• Small aluminum and fiberglass boats (20° transom angle)—
Use the 9° shim with the taper up (see Figure 4). If your boat is
capable of speeds above 20kn (28MPH), install the bracket
with only the 4.5
° shim, taper up.
• If you are unsure about using the shim(s)—Experiment with
the shims by following the instructions “Mounting & Adjusting.”
Mounting & Adjusting
CAUTION: Do not position the leading edge of the sensor lower
than the trailing edge because aeration will occur.
CAUTION: Do not position the sensor deeper into the water than
necessary to avoid increasing drag, spray, and water noise and
reducing boat speed.
1. Apply marine sealant to the threads of two, #10 x 1-1/4", self-
tapping bracket screws to prevent water seepage into the
transom. Be sure the nuts are in the slots in the back of the
bracket and any shim(s) is in place (see Figure 1). Screw the
sensor to the hull (see Figure 5). Do not tighten the screws
completely at this time.
2. Using a straight edge, sight the underside of the sensor relative to
the underside of the hull (see Figure 4). The trailing edge of the
sensor must be 1 – 6mm (1/16 – 1/4") below the leading edge.
3. Using the vertical adjustment space in the bracket slots, slide
the sensor up or down until the bottom left corner of the sensor
projections 0 – 3mm (0 – 1/8") below the bottom of the hull (see
Figure 3). When you are satisfied with the position of the
sensor, tighten the two bracket screws.
Testing on the Water
1. With the beam angle factory-set to 90 ° , become familiar with
your echosounder’s performance at a speed of 4kn (5MPH).
2. Gradually increase the boat speed and observe the gradual
decline in performance due to turbulent water flowing over the
sensor’s active surface.
• For the best performance, the transducer’s face must be in contact
with smooth water. To identify an area of “clean” water, observe
the water flow off the transom while the boat is underway.
• Allow headroom space above the bracket for it to release and
rotate the sensor upward.
• Mount the sensor as close to the centerline (keel) of the boat as
possible to ensure the transducer’s face remains in the water
when the boat is turning.
• Single drive boat—Mount at least 75mm (3") beyond the
swing radius of the propeller, so the water passing over the
transducer does not cause a flow disturbance to the propeller
(see Figure 2). The starboard side where the propeller blades
are moving downward is preferred.
• Twin drive boat—Mount the sensor between the drives.
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 location, position the sensor, so it projects 3mm
(1/8") below the bottom edge of the transom (see Figure 3).
2. Being sure the bottom of the sensor is parallel to the waterline,
mark the location of the screw holes with an “X” in the center of
the two outer most slots.
3. Using a 4mm, #23, or 9/64" drill bit, drill two holes 22mm (7/8")
deep at the locations indicated.
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 (13 ° transom angle)—The bracket is
designed for a standard 13 ° transom angle. The 9 ° shim is not
needed for this installation. If your boat is capable of speeds
above 20kn (28MPH), install the bracket with the 4.5° shim,
taper down (see Figure 4).
• Stepped transom and jet boats (3 ° transom angle) —Use the 9 °
shim with the taper down (see Figure 4). If your boat is capable of
speeds above 20kn (28MPH), install the bracket with both the 9
°
and 4.5 ° shims, taper down. Install the 4.5 ° shim against the
transom after shaving the interfering portion of the rails and lower
bump. Place the 9
° shim and bracket assembly on top.
2
Figure 3. Vertical adjustment and cable routing
50mm (2")
cable cover
Hull projection
0–3mm (0–1/8")
parallel to
cable clamp
waterline
Copyright © 2008 - 2012 Airmar Technology Corp.
(3”) of slack
to adjust
beam angle
75mm (3")
minimum beyond
swing radius
Figure 2. Mounting location on single drive boat
Copyright © 2008 Airmar Technology Corp.
NOTE: Starboard
side of hull where
propeller blades are
moving downward is
preferred.
screw (2)
location