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OWNER’ S GUIDE & INSTALLATION INSTRUCTIONS
Cavity or Welded-tank Mount: 1kW
Sealcast™ Depth Transducer
Chirp Models:
CM265LH, CM265LM, CM275LHW
Patent http://www.airmar.com/patent.html
WARNING: The transducer must be professionally installed
using accepted practices. The cavity or welded tank must be
strong and watertight to reduce the risk of property damage,
D-19793-rev.1 101790-rev.1 01/08/21
personal injury, and/or death.
Follow the precautions below for optimal product
performance and to reduce the risk of property
damage, personal injury, and/or death.
Record the information found on the cable tag for future reference.
Part No._________________Date___________Frequency________kHz
CAUTION: Never use solvents. Cleaners, fuel, sealants,
paint, and other products may contain solvents that can
damage plastic parts, especially the transducer’s face.
WARNING: Always wear safety glasses, a dust mask,
and ear protection when installing.
WARNING: Use marine sealant to seal the hull and
hold the transducer firmly in place. When the boat is
underway, especially at high speeds, water will enter
any gaps and push against the transducer with
considerable force.
WARNING: A faceplate is required to secure the
transducer to the hull. The bolts are an aid to
installation only and must not be solely relied upon.
When the boat is underway, especially at high speeds,
water will push against the transducer with
considerable force.
WARNING: Immediately check for leaks when the
boat is placed in the water. Do not leave the boat
unchecked for more than three hours. Even a small
leak may allow considerable water to accumulate.
CAUTION: Always operate the transducer in water.
Operating in air will allow the transducer to overheat
resulting in failure.
CAUTION: Do not install in the engine compartment or
other hot place. The transducer may fail if it overheats.
CAUTION: The transducer must be flush with the
bottom of the hull for good performance.
CAUTION: Never pull, carry, or hold the transducer by
the cable. This may sever internal connections.
CAUTION: Never strike the transducer.
CAUTION: Never power sand or pressure wash the
transducer. It may weaken the structure or damage
the internal components.
IMPORTANT: Please read the instructions completely
before proceeding with the installation. These instructions
supersede any other instructions in your instrument
manual if they differ.
Applications
• Cavity mounting recommended for fiberglass hulls.
• Cavity mounting recommended for high-speed boats.
Tools & Materials
NOTE: Making a fiberglass cavity in the hull, a faceplate, or a
welded tank requires additional tools and materials not listed.
Safety glasses
Dust mask
Ear protection
Scissors
Masking tape
Electric drill
Drill bits and hole saws:
Pilot hole Ø 3mm or 1/8"
Cable hole large enough to accommodate the bushing
Bolt hole (3) Ø 8mm or 5/16"
Sandpaper (coarse grit 120)
Tack cloth
Marine sealant (suitable for below waterline)
Purchased nuts, bolts & washers (3)
(stainless steel, 1/4"-20 UNC threads)
Torque wrench
Grommet(s) (some installations)
Cable ties
Water-based anti-fouling coating (mandatory in salt water)
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displacement hull
outboard and I/O
Figure 1.
stepped hull
inboard
Best location for the transducer
Copyright © 2006 Airmar Technology Corp.
3. Create a strong watertight cavity to hold the transducer.
Making a Faceplate
A faceplate is required to ensure the transducer is held within the
cavity when the boat is traveling at high speed.
1. Make a faceplate using a strong material suitable for below the
waterline such as 316 stainless steel or glass-fiber reinforced
epoxy FR4 or G10. The faceplate must be thick enough to fill the
lip of the transducer [6mm (1/4")] after marine sealant is applied.
2. Cut the opening in the faceplate using the template supplied.
Follow the “Transducer lip: cutting line for the opening in the
faceplate.”
3. Drill holes for the fasteners that will hold the faceplate securely
to the hull. Fasteners must be suitable for below waterline.
Mounting Location
Placement Guidelines
CAUTION: Do not mount the transducer in line with or near water
intake or discharge openings or behind strakes, fittings, or hull
irregularities that will disturb the water flow.
CAUTION: Do not mount the transducer in line with trailer rollers
or bunks that may damage the transducer’s face.
Choose a Location
• Where the hull is flat or nearly flat, so the transducer beam will
be aimed straight down.
• Where the water flowing under the hull is smoothest with a
minimum of bubbles and turbulence (especially at high speeds).
• Where the transducer will be in contact with the water at all times.
• Where the transducer beam will not be blocked by the keel or
propeller shaft(s).
• In a cool well-ventilated area away from the engine to avoid
overheating.
• Away from interference caused by power and radiation sources
such as: the propeller(s) and shaft(s), other machinery, other
echosounders, and other cables. The lower the noise level, the
higher the echosounder gain setting that can be used.
• Where there is working space inside the vessel.
Hull Types (Figure 1)
• Displacement hull powerboats—Locate amidships near the
centerline. The side of the hull where the propeller blades are
moving downward is preferred.
• Planing hull powerboats—Mount well aft and well inboard of
the first set of lifting strakes to ensure that the transducer will be
in contact with the water at high speeds. The side of the hull
where the propeller blades are moving downward is preferred.
Outboard and I/O—Mount just forward of the engine(s).
Inboard—Mount well ahead of the propeller(s) and shaft(s).
Stepped hull—Mount just ahead of the first step.
Dry Fitting
The transducer must be flush with the bottom of the hull for good
performance. Dry fit the transducer in the cavity before installing.
1. Position the template (page 4) within the cavity. Tape it in place.
2.
Using the appropriate drill bits, drill a hole through the cavity for
the cable
.
3. From outside the hull, thread the transducer cable through the
hole in the mounting cavity (Figure 2). Push the transducer into
the cavity as far as possible.
Measure the gap between the face of transducer and the outside
of the hull (as if the transducer is flush to the exterior hull
surface). This will be the thickness of marine sealant that must
be applied to the cable side of the transducer, plus an additional
3mm (1/8") to fill any empty spaces.
Bedding & Installing
CAUTION: Be sure the surfaces to be bedded are clean and dry.
1. To ensure that the marine sealant will adhere properly, sand the
area around the hole in the hull, inside and outside. On the
transducer, sand all the surfaces that will contact the hull. Sand
the lip of the transducer (Figure 2). Do not sand the face. Remove
all dust using a tack cloth. Do not use alcohol on the transducer.
cable
Installation in a Welded Tank
Each hull is different. Professionally install the transducer
following accepted practices.
Installation in a Cavity
Pre-molded Cavity
If the boat has a pre-molded cavity in the hull to receive the
transducer, go to “Making a Faceplate”.
Making a Cavity
1. Using the template (page 4), cut along the “cutting line for hull
cavity“ (outermost line). Tape it to the hull at the selected
mounting location.
2. Cut a hole in the hull.
2
cavity
hull
transducer
lip
face
Figure 2. Dry fitting
Copyright © 2021 Airmar Technology Corp.
thickness of marine
sealant to be applied
to the cable side
of the transducer
plus 3mm (1/8")
to fill any empty spaces
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2. Apply marine sealant to the following
surfaces to seal the hull and hold the
transducer firmly in place (Figure 3):
• Cable side of the transducer—Apply
the amount of marine sealant
determined by dry fitting the transducer
washer (3)
in the cavity, plus an additional 3mm (1/8").
• Apply 6mm (1/4") of marine sealant to
the transducer surfaces that will contact
the cavity, including the lip.
• Apply 6mm (1/4") of marine sealant to
the cable fittings, being sure the marine
cavity
sealant extends 6mm (1/4") outside of
the cavity and into the hull.
• Apply 3mm (1/8") of marine sealant to
the threads of the purchased bolts.
• Apply 3mm (1/8") of marine sealant to
the surface of the purchased washers
that will contact the cavity.
• Apply 3mm (1/8") of marine sealant to
the side of the faceplate that will
contact the hull and the transducer’s lip.
fastener
(4 or more)
faceplate
• Apply 3mm (1/8") of marine sealant to
the fasteners that will hold the faceplate
to the hull.
3. From outside the hull, thread the transducer cable through the
hole in the mounting cavity. Push the transducer into the
mounting cavity and seat it firmly within the recess.
The
transducer’s face must be flush with the outside of the hull for
good performance. If necessary, apply additional marine sealant
to the cable side of the transducer.
4. From inside the hull, screw a nut onto each bolt. Place one
washer against each nut so that the side with the sealant will be
against the cavity when installed. Screw each bolt into a
threaded hole in the transducer. Tighten the bolts using a torque
wrench with a force not exceeding 85 in.-lb. Do not over tighten.
5. When the boat is underway, especially at high speeds, water
will enter any gaps between the transducer and the hull and
push against the transducer with considerable force. From
outside the hull, fill any gaps between the transducer and the
cavity with marine sealant.
6. Fasten the faceplate to the hull.
7. Remove the excess sealant on the outside of the hull to ensure
smooth water flow under the transducer.
Cable Routing & Connecting
CAUTION: If the transducer came with a connector, do not
remove it to ease cable routing. If the cable must be cut and
spliced, use Airmar’s splash-proof Junction Box No. 33-035 and
follow the instructions provided. Removing the water-proof
connector or cutting the cable, except when using water-tight
junction box, will void the transducer warranty.
1. Route the cable to the echosounder being careful not to tear the
cable jacket when passing it through the bulkhead(s) and other
parts of the boat. Use grommets to prevent chafing. To reduce
electrical interference, separate the transducer cable from other
electrical wiring and the engine(s). Coil any excess cable and
secure it in place with cable ties to prevent damage.
2. Refer to your echosounder owner’s manual to connect the
transducer to the instrument.
NOTE: Dark areas
show marine sealant.
face
bolt, nut &
cable
transducer
Figure 3. Bedding and installing
Copyright © 2021 Airmar Technology Corp.
Checking for Leaks
When the boat is placed in the water, immediately check around
the transducer for leaks. Note that very small leaks may not be
readily observed. Do not leave the boat in the water for more than
3 hours before checking it again. If a leak is observed, repeat the
installation procedure immediately.
Maintenance & Replacement
Anti-fouling Coating
Surfaces exposed to salt water must be covered with an antifouling coating. Use a water-based anti-fouling coating made for
transducers only. Never use ketone based anti-fouling paint, since
ketones can attack many plastics possibly damaging the
transducer. Brush on anti-fouling coating every 6 months or at the
beginning of each boating season.
Cleaning
Aquatic growth can accumulate rapidly on the transducer’s face,
reducing its performance within weeks. Clean the surface with a
®
Scotch-Brite
scour and mild household detergent, being careful
to avoid making scratches. If the fouling is severe, lightly wet sand
it with fine grade wet/dry paper.
Transducer Replacement & Parts
The information needed to order a replacement Airmar 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 near the top of page one.
Obtain parts from your instrument manufacturer or marine dealer.
Gemeco
Airmar EMEA
USA
Tel: 803-693-0777
Email: sales@gemeco.com
Europe, Middle East, Africa
Tel: +33.(0)2.23.52.06.48
Email: sales@airmar-emea.com
marine
sealant
hull
35 Meadowbrook Drive, Milford, New Hampshire 03055-4613, USA
•
www.airmar.com
Copyright © 2021 Airmar Technology Corporation. All rights reserved.
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bolt (3)
8mm or 5/16"
cutting line for hull cavity
transducer outline
transducer lip and cutting line for opening in faceplate
100mm
(3.94")
184mm
(7.24")
120mm
(4.72")
164mm
(6.46")
cable
Template
CM265LH, CM265LM, CM275LHW
IMPORTANT: Some printers and
printer settings can alter the size of
the template.
Verify the template’s size before
cutting. Place the transducer on the
template to be sure it is the exact
size. If necessary, redraw the
template.
6mm
(0.25")
10mm
(0.4")
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