Airmar M42 - Manual (Page 3)

Installing the Fairing & Transducer
M172 —Follow separate installation instructions on page 3.
Warning: The fairing must be installed parallel to the keel to
ensure proper boat handling and water flow over the transducer.
1. Locate the hole for the forward threaded rod (see Figures 3 & 6).
Hold the fairing against the hull, being sure the arrow/blunt end
points forward toward the bow and the stuffing tube is centered
inside the cavity. With the fairing parallel to the centerline of
the boat (keel) , use the forward hole in the fairing as a guide.
Drill the 11mm or 7/16" diameter hole through the hull for the
threaded rod.
Do not drill the second hole at this time.
2. Temporarily fasten the fairing to the hull with one of the
threaded rods. With the fairing parallel to the centerline of
the boat (keel) , use the aft hole in the fairing as a guide. Drill
the 11mm or 7/16" diameter hole through the hull for the
remaining threaded rod.
3. Remove the temporary threaded rod. Clean and sand the area
around the holes, inside and outside, to ensure that the marine
sealant will adhere properly. Remove any petroleum residue with
a mild household detergent or a weak solvent such as alcohol.
Metal hull —Remove all burrs with a file and sandpaper
Welded steel stuffing tube with conduit only —It is easier to
seal the cable inside the stuffing tube before the transducer and
fairing are attached to the hull. Follow the instructions that came
with your stuffing tube.
4. Apply a 2mm (1/16") thick layer of marine sealant to the surface
of the fairing that will contact the hull (see Figures 6 & 7).
5. Apply a 2mm (1/16") thick layer of marine sealant to each
threaded rod. The marine sealant will seal the hull and hold the
nuts securely in place. Screw a nut and slide a stainless steel
washer onto each threaded rod. Position the nuts a distance
from the rod ends equal to dimension “A”. Slide the threaded
rods through the fairing.
Note : The rods will extend above and below the fairing .
6. Place the fairing against the hull, pushing the threaded rods
through the hull. With a person stationed inside the vessel,
position the backing block on the rods. Secure each rod with a
stainless steel washer and nut (see Figure 8). Tighten the nuts
with a torque wrench using a force not exceeding 7 N-m (5 ft.-lb.).
Aluminum hull — Be sure the rods are isolated from the hull to
prevent electrolytic corrosion.
Caution : Never pull, carry, or hold the transducer by its cable as
this may sever internal connections.
7. Thread the transducer cable through the cavity in the fairing and
the stuffing tube to the inside of the hull. Apply a 2mm (1/16")
thick layer of marine sealant to the surface of the transducer that
will contact the fairing. Push the transducer onto the threaded
rods (see Figures 6 & 7).
8. Mount the transducer to the fairing by sliding a rubbery washer
and stainless steel washer onto each threaded rod and
securing them with a nut. Tighten the nuts with a torque wrench
using a force not exceeding 12 N-m (10 ft.-lb.).
Note : The rods should extend a minimum of 3 threads beyond
the nut after it is tightened. Be sure there is marine sealant on
the exposed threads.
9. Plug the mounting holes to minimize turbulence on the surface
of the transducer. Cut the foam plugs to length so that each
plug will be recessed 5mm (3/16") below the surface of the
housing. Push the foam plugs into the holes. Use marine
sealant to fill each recess
FLUSH with the transducer’s surface.
10.Remove excess sealant on the outside of the hull and the
fairing to ensure smooth water flow over the transducer.
Sealing & Routing the Cable
To form a watertight seal inside the stuffing tube, follow the
installation instructions that came with your stuffing tube.
Route the cable to the echosounder being careful not to tear the
cable jacket when passing it through the bulkhead and other parts of
the boat. To reduce electrical interference separate the transducer
cable from other electrical wiring and the engine. Refer to your
echosounder owners manual to connect the cable to the instrument.
Checking for Leaks
Warning : Never install a transducer and leave the boat in the
water unchecked for several days.
When the boat is placed in the water, immediately check around
the stuffing tube and the rods that fasten the transducer to the hull
for leaks. Note that very small leaks may not be readily observed. It
is best not to leave the boat in the water unattended for more than 3
hours before checking it again. If there is a small leak, there may be
considerable bilge water accumulation after 24 hours.If a leak is
observed around the stuffing tube, tighten the compression nut
another quarter turn and see if the leakage stops. If there is a leak
around the threaded rods or the outside of the stuffing tube, repeat
the installation and sealing procedures
immediately .
Maintenance & Replacement
Antifouling Paint
Surfaces exposed to salt water must be coated with antifouling
paint. Use water-based antifouling paint only. Never use ketone
based antifouling paint, since ketones can attack many plastics
possibly damaging the transducer.
Cleaning
Aquatic growth can accumulate rapidly on the transducer’s face,
reducing its performance within weeks. Clean it using a Scotch-
Brite® scour pad and mild household detergent,
being careful to
avoid making scratches. In severe cases, lightly wet sand the
surface with fine grade wet/dry paper.
Replacement
Contact your marine dealer or echosounder manufacturer to
obtain 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 on the top of page one.
3
marine
sealant
model dimension “A”
M155 28kHz 54mm (2.13")
M155 38kHz 45mm (1.75")
R155 45mm (1.75")
M177 86mm (3.38")
AIRMAR ®
dimension “A”
Figure 7. Marine sealant —detail shown