Airmar P72 User Manual

INSTALLATION INSTRUCTIONSOWNER’S GUIDE &

In-Hull & Trolling Motor

Puck Transducer

Models: P72, P76, P78

Follow the precautions below for optimal
product performance and to reduce the risk of
property damage, personal injury, and/or death.

WARNING: Always wear safety goggles and a dust

mask when installing.

17-010 rev.11 09/21/12

CAUTION: Chose the transducer designed for your
boat’s deadrise angle. Never use adhesive to fill gaps
between the transducer and the hull since this will
greatly reduce the transducer’s performance.

CAUTION: The fiberglass hull below the transducer
must be SOLID. The transducer will not transmit
through coring material such as foam or balsa wood.

CAUTION: Never pull, carry, or hold the transducer by
the cable. This may sever internal connections.

Record the information found on the cable tag for future reference.

Part No._________________Date___________Frequency________kHz

P72

P78

P76

Applications

• Fiberglass hulls only

• Recommended for high-speed boats

• P72 and P76 accommodate a deadrise angle of 10

• P78 accommodates a deadrise angle of 10° – 22°

° or less

CAUTION: Never use solvents. Paint, sealants,
cleaners, fuel, and other products may contain
solvents that can damage plastic parts, especially
connectors.

IMPORTANT: Please read the instructions completely
before proceeding with the installation. These
instructions supersede any other instructions in your
instrument manual if they differ.

In-Hull Mount

Tools & Materials

Safety goggles
Dust mask
Duct tape
Pole
Detergent (some installations)
Weak solvent (such as alcohol)
Disk sander (some installations)
Thin sealable plastic bag (some installations)
Cable ties

®

Water-based lubricant (such as K-Y
Grommet(s) (some installations)
Installation in a cored fiberglass hull:

Electric drill
Hole saw 78 mm or 3"
Miniature disk sander (such as Dremel Moto-Tool)
Casting epoxy (such as Polypoxy #7035/7040 by Pettit)
Paper cup
Stirrer

jelly) (some installations)

Mounting Location

About Fiberglass Hulls

Since the hull absorbs acoustic energy, transmitting through the
hull reduces the transducer’s performance. Fiberglass hulls are
often cored in places for added strength or to reduce weight. These
cored areas contain balsa wood or structural foam which are poor
sound conductors. Do not locate the transducer over coring.

Placement

CAUTION: Do not mount the transducer near water intake or
discharge openings or behind strakes, fittings, or hull irregularities
that will disturb the water flow.

Choose a location:

• Where the fiberglass is SOLID (no air bubbles are trapped in
the fiberglass resin) and where no coring, flotation material, or
dead air space is sandwiched between the inside skin and outer
skin of the hull.

• Where the hull below the transducer will be in contact with the
water at all times.

• Where the water flowing under the hull is smoothest with a
minimum of bubbles and turbulence (especially at high speeds).

• 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 the transducer beam will not be blocked by the keel or
propeller shaft(s).

• Where there is adequate space inside the vessel for
installation.

Outboard Inboard/outboard

Inboard Sailboat

Figure 1. Selecting the mounting location

Copyright © 2005 Airmar Technol ogy Corp.

Boat Type (see Figure 1)

Consult the boat manufacturer for the best transducer placement.
If this information is unavailable, follow the guidelines below.
When possible, mount on the side of the hull where the propeller
blades are moving downward.

• Outboard powerboats—Install as far aft as is practical.

• Inboard/outboard powerboats—Install close to the engine(s).

• Inboard powerboats—Install forward of the propeller(s) and
shaft(s).

• Sailboats—Install on or near the centerline and forward of any
fin keel 300 - 600mm (1 - 2').

cable

pole

active face

Figure 2. Establishing a performance baseline

Copyright © 2005 Airmar Technology Cor p.

ABC

Testing the Selected Mounting Location

Establishing a Performance Baseline

The results of this test are used as a basis of comparison to
determine the best in-hull location for the transducer.

1. Take the boat to the maximum depth in which you will be
operating the echosounder. If deep water is not available, find a
location with at least 15m (50').

2. Connect the transducer to the echosounder.

3. Tape the transducer to a pole, cable side up. Do not tape over
the active face. Hold the transducer over the side of the boat
with the active face fully submerged and parallel to the water
surface (see Figure 2).

4. Observe the echosounder’s performance and the gain setting
required to obtain a reading on the display. Record the depth
reading.

Testing the Location

While the boat is at the same site (depth of water), test the
transducer inside the hull at the mounting location. Use one of the
test methods below.

A.For a location near the stern and a minimal deadrise angle—

Clean away any build-up of grease and/or dirt with detergent or
alcohol. Place the transducer against the hull and allow bilge
water to cover the surface where they touch (see Figure 3A).

B.For a greater deadrise angle—If the hull surface is not smooth,

grind it with a disc sander. Place the transducer inside a thin
plastic bag. Partially fill the bag with water and close it tightly with
a cable tie. Wet the surface of the hull and press the active face
of the transducer against it through the bag (see Figure 3B).

C.For any location—If the hull surface is not smooth, grind it with

a disc sander. Coat the face of the transducer with a water-
based lubricant (such as K-Y® jelly). With a twisting motion,
press the face against the hull (see Figure 3C) After testing,
wipe all traces of the lubricant from the transducer’s face.

Observe the echosounder’s performance and compare it to the
baseline. Look for a stable depth reading that is similar to the
baseline. Compare the thickness and intensity of the bottom trace.

If the performance is close to the baseline, this is a good mounting
location. Remember, energy is lost transmitting through the hull. If
the test reading differs markedly from the baseline, you will need
to find another location to install the transducer.

NOTE: If there is no reading or it is erratic, the transducer may be
positioned over coring that is absorbing the acoustic energy.
Choose another location. If no other spot is available, check with
the boat manufacturer to be certain coring is present before
proceeding with the instructions for “Installation in a Cored
Fiberglass Hull” on page 4.

Selecting the Adhesive

CAUTION: Do not use:

• “5 minute” epoxies because they are too brittle.

• RTV (silicone) adhesives because they absorb most of the

sound energy.

A hard adhesive, like the epoxy supplied, transmits sound best.
However, winter temperature extremes and flexing on trailer
rollers can cause it to delaminate. Soft adhesives absorb sound
and will greatly reduce performance. To compromise, use a
viscous slow-cure epoxy or a fairly rigid one-part adhesive

Figure 3. Testing at the selected location

Copyright © 2005 Airmar Technology Cor p.

sealant. In cold climates, a one-part polyurethane adhesive, such

®

as Boat-Life’s Life Seal

, may be best.

2