Furuno 525T-BSC, 525T-BSD Installation Instructions

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OWNER’S GUIDE & INSTALLATION INSTRUCTIONS

Thru-hull Metal Stem Depth Transducer

Models: B39, B45, B46, B49, B240,

B250, B256, B260, SS505

IMPORTANT : Please read these instructions

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

CAUTION : NEVER USE SOLVENTS

Cleaners, fuels, paint, sealants, and other products may
contain strong solvents, such as acetone, which can attack

17-008-05 rev. 04 12/01

many plastics greatly reducing their strength.

Applications

•

Bronze housing

Caution

electrolytic corrosion will occur.

•

Stainless steel housing

•

Aluminum or steel hull

prevent electrolytic corrosion.

Caution

stainless steel sensor from a metal hull.

•

Caution

positive ground system

: Ne ver mount a bronz e housing in a metal hull, because

: Installation requires using a fairing kit to isolate the

: Never install a metal housing on a vessel with a

Tools and Materials

Fairing (
Digital level
Safety goggles
Dust mask
Band saw
Rasp
Electric drill
Drill bits:

Sandpaper
Mild household detergent
Marine sealant
Slip-joint pliers
Zip-ties
Water-based antifouling paint (
Installation in a cored fiberglass hull: (see page 3)

mandatory for SS505

or

power tool (installation with a fairing)

Pilot hole 3mm
B39, B49 26mm or 1"
B45, B46, SS505 22mm
B240, B250, B260 33mm
B256 30mm

Drill bit for hull interior:
B39, B49 37mm, 38mm,
B45, B46, SS505 35mm
B240, B250, B260 42mm
B256 40mm, 41mm,
Cylinder, wax, tape, and casting epoxy

recommended for fiberglass or wood hulls only.

is compatible with all hull materials.

—Use a stainless steel housing to

.

)

or

bubble level & protractor (installation w/ fairing)

or

hand saw (installation with a fairing)

or

1/8"

7/8"
1-5/16"

or 1-3/16"

weak solvent (alcohol)

mandatory in salt water )

1-1/2"
1-3/8"
1-5/8"

1-5/8"

Record the information found on the cable tag f or future reverence.

Part No._________________Date___________Frequency________kHz

B45

standard fairing

Identify Y our Model

The model name is printed on the cable tag.

Mounting Location

Acoustic Noise

Acoustic noise is always present and these sound waves can
interfere with the operation of the transducer. Background noise
from sources such as: waves, fish, and other vessels cannot be
controlled. However, carefully selecting the transducer mounting
location can minimize the affect 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

Choose a location where:

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

• The transducer will be continuously immersed in water.

• The transducer beam is unobstructed by the keel or propeller
shaft(s).

• There is a minimum deadrise angle.

• There is adequate headroom inside the vessel for the height of
the housing and tightening the nut.

Caution : Do not mount the sensor:

Near water intake or discharge openings
Behind strakes, fittings, or hull irregularities
Behind eroding paint (an indication of turbulence)

Boat Types

•

Displacement hull powerboat —Locate 1/3 aft LWL and

150–300mm (6–12") off the centerline on the side of the hull
where the propeller is moving downward.

•

Planing hull powerboat —Mount well aft, on or near the

centerline, and
insure that the transducer is in contact with the water at high
speeds. Mount on the side of the hull where the propeller is
moving downward.

Outboard and I/O —Mount just forward of the engine(s).
Inboard —Mount well ahead of the propeller(s) and shaft(s).
Step-hull —Mount just ahead of the first step.
Boat capable of speeds above 25kn (29MPH)—Review

sensor location and operating results of similar boats before
proceeding.

•

Fin keel sailboat —Mount to the side of the centerline and

forward of the fin keel 300–600mm (1–2').

•

Full keel sailboat —Locate amidships and away from the keel

at the point of minimum deadrise angle.

(see Figure 1)

well inboard of the first set of lifting strakes to

1/3 aft

LWL

(Load Waterline Length)

outboard and I/O

step-hull

displacement hull

planning hulls

fin keel sailboat

pressure waves

150-300mm
(6-12")

inboard

Hull Thickness

(measured perpendicular to the waterline)

Minimum Maximum Maximum
Model
B39, B49 19mm (
B45 6mm (
B46 19mm (
B240 32mm (1
B250, B256, B26019mm (
SS505 6mm (

Installation

no fairing no fairing with fairing

3

⁄

4

") 98mm (3

1

⁄

4

") 92mm (2

3

⁄

4

") 88mm (3

1

⁄

4

") 152mm (6") 83mm (3

3

⁄

4

") 114mm (4

1

⁄

4

") 104mm (4

7

⁄

8

") 50mm (2")

5

⁄

8

") 50mm (2")

1

⁄

2

") 40mm (1

1

⁄

2

1

⁄

8

") 45mm (1
") 56mm (2

(no fairing or standard fairing only)

5

⁄

8

1

⁄

4

3

⁄

4

1

⁄

4

WARNING : High-speed fairing must be installed following the

Installation Instruction Supplement that comes with the fairing.
The high-speed fairing requires an anti-rotation bolt. Failure to
install the anti-rotation bolt may result in the fairing rotating while
the boat is underway. The effect may be violent movement and
loss of steering. This could result in serious injury or death to
passengers and/or damage to the boat or other property.

Metal hull —The SS505 must be isolated from a metal hull. For

your safety you m ust follo w the Installation Instruction Supplement
provided with the fairing.

Cored fiberglass hull —Follow separate instructions on page 4.
No fairing —If you are installing a transducer without a fairing,

disregard all references to a fairing.

")
")
")
")

full keel sailboat

Figure 1.

Best location for the transducer

About Fairings

Nearly all vessels have some deadrise angle at the 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. A fairing is strongly recommended if the deadrise angle
exceeds 10 °

• Orients the sound beam straight down by mounting the
transducer parallel to the water surface

• Minimizes aerated water flowing over the transducer’s face by
mounting it deeper in the water

Airmar Urethane Fairing

Made of a high impact urethane with an integrated cutting guide,
an Airmar fairing is safer and easier to cut with a band saw and
shape with hand tools than custom fairings. It can be shaped to
accommodate a deadrise angle of up to 25 °
numbers, see “Replacement Parts” on page 4.)

Backing Block

(see Figure 2).

. (For fairing part

Cutting the Fairing

High speed fairing —For your safety it is mandatory to follow the

Installation Instruction Supplement that comes with the fairing.

1.Measure the deadrise angle of the hull at the selected location
using a digital level, or b ubb le le vel and protr actor (see Figure 2)

2.Tilt the band saw table to the measured angle and secure the
cutting fence (see Figure 3).

3.Place the fairing on the table so the cutting guide rests against
the fence. The arrow will be pointing toward you for installation
on the port side and away from you for installation on the
starboard side of the boat (see Figures 3 and 4).

Notice : The ARROW always points forward toward the bow.

(A symmetrical fairing can be oriented either way.) Be sure to
orient the fairing on the band saw so the angle cut matches the
intended side of the hull and not the mirror image.

cable

stem

hull nut

backing block

fairing thickness

6–12mm (1/4–1/2")

Aft View

hull

slope of hull

parallel to
waterline

deadrise
angle

A backing block is mounted inside the hull to provide a level
surface for the hull nut to seat against (see Figure 2). It is
fabricated matching the interior deadrise angle of the boat. After
cutting an Airmar fairing, use the remaining section as the backing
block.

2

marine

standard fairing

sealant

Figure 2. Bedding and installing (B45 with std. fairing shown)