Sealcast M42 Owner's Manual

OWNER' S GUIDE & INSTALLATION INSTRUCTIONS
Sealcast Transducer
™
Models: M42 and M163
IMPORTANT : Please
completely before proceeding with the installation.
These instructions supersede any other instructions in
your instrument manual if they differ.
CAUTION : NEVER USE SOLVENTS
Cleaners, fuel, paint, sealants, and other products may
contain strong solvents, such as acetone, which attack
many plastics greatly reducing their strength.

Mounting Location

Acoustic Noise

Acoustic noise is always present and these sound waves can
interfere with the operation of the transducer. Ambient
(background) noise from sources such as: waves, fish, and other
vessels cannot be controlled. However, carefully selecting the
transducer's mounting location can minimize the effect of vessel
generated noise from the propeller(s) and shaft(s), other
machinery, and other echosounders. The lower the noise level,
the higher the echosounder gain setting that can be used.

Placement

Carefully study the hull to determine the best mounting location.
• Mount the transducer away from the propeller and other
sources of vessel generated noise (see Figure 1).
• Mount where the water is smoothest with a minimum of turbulence
and bubbles. Water near the bow and keel can be quite aerated.
• Locate the transducer about 1/3 aft LWL. Generally, this
provides the best compromise between obtaining aeration-free
water away from the bow and minimizing propeller noise.
• Mount the transducer on the side of the hull where the
propeller(s) is moving downward. The upward motion of the
propeller generates pressure waves and pushes bubbles up
against the hull. By mounting on the downward side, the hull
shades the transducer from this effect (see Figure 2).
• The deeper the transducer protrudes into the water, the less
aeration.
3˚ incline
angle
(Load Waterline Length)
Figure 1. Recommended transducer location & incline angle
read these instructions
1/3 aft
LWL
Record the information found on the cable tag for future reference.
Part No._________________Date___________Frequency________kHz
fairing
deadrise shape
Figure 3. Fairing and backing blocks
• Do not mount the transducer in an area of turbulence or bubbles:
Near water intake or discharge openings
Behind strakes, fittings, or hull irregularities
Behind eroding paint (an indication of turbulence)

External Mount

Fairing and Backing Block

Nearly all vessels have some deadrise angle at the transducer's
mounting location. If the transducer is mounted directly to the hull,
the sound beam will be tilted off the vertical at the same angle as
the deadrise. If the deadrise angle at the mounting location
exceeds 10 ° a fairing is strongly recommended (see Figure 2).
• Orients the sound beam straight down by mounting the
transducer parallel to the water's surface
• Minimizes aerated water flowing over the transducer's face by
mounting it deeper in the water
• Inclines the transducer so the acoustic window is shaded from
propeller noise. A 3 • incline angle is recommended (see Figure 1).

Fabricating a Fairing and Backing Blocks

Measure the deadrise angle of the hull at the selected location
(see Figure 2). A fairing is usually constructed of an oily wood
such as mahogany or teak. Shape the fairing to match the outline
of the transducer housing. Orient the fairing with the blunt end
facing forward toward the bow. Cut the fairing to match the hull's
deadrise angle and shape it as precisely as possible to the hull.
Cut a 75mm x 150mm (3" x 6") hole in the center of the fairing for
the stuffing tube and the cable service loop. Place the transducer
over the fairing and using the transducer as a guide, drill two holes
for the threaded rods (see Figure 3).
Transom View
pressure waves
aeration, cavitation and turbulence
Figure 2. Deadrise angle & recommended transducer location
backing block (2)
blunt
77mm (3")
77mm (3")
end
deadrise shape
hole diameter
M42—13mm (1/2")
M163—10mm (3/8")
slope of hull
deadrise angle
parallel to waterline
fairing minimizes aerated
water flowing over the
transducer's face by
mounting it deeper
in the water