Airmar S300 User Manual

INSTALLATION INSTRUCTIONSOWNER’S GUIDE &

Thru-Hull, Shorty™ with Valve

Speed & Temperature Sensor

Models: S300, ST300

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.

WARNING: The valve is not a watertight seal! Always

17-274-01 rev. 04 04/14/11

use the insert or the blanking plug secured with the
safety wire for a watertight seal.

WARNING: The O-rings must be intact and well
lubricated to make a watertight seal.

WARNING: Always attach the safety wire to prevent
the sensor insert or blanking plug from backing out in
the unlikely event that the cap nut fails or is screwed
on incorrectly.

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: Never use a fairing with a plastic housing;
the protruding sensor would be vulnerable to damage
from impact.

CAUTION: Never pull, carry, or hold the sensor by its
cable; this may sever internal connections.

CAUTION: Never use solvents. Cleaners, fuel,
sealants, paint, and other products may contain strong
solvents, such as acetone, which attack many
plastics, greatly reducing their strength.

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

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

Part No.:___________________Date___________

Low Profile P371

Flush P398

Pretest

Connect the sensor to the instrument and spin the paddlewheel.
Check for a speed reading (and the approximate air temperature if
applicable). If there is no reading(s), check all the connections
and repeat the test. If there is still no reading(s) or it is inaccurate,
return the product to the place of purchase.

Tools & Materials

Safety goggles
Dust mask
Water based anti-fouling paint (mandatory in salt water)
Electric drill with minimum 10mm (3/8") chuck capacity
Drill bit 3mm or 1/8"
Hole saw 51mm or 2"
Countersink tool (installing a P398 flush housing)
Sandpaper
Mild household detergent or weak solvent (such as alcohol)
File (installation in a metal hull)
Marine sealant (suitable for below waterline)
Additional washer [aluminum hull less than 6mm (1/4") thick]
Grommet(s) (some installations)
Cable ties
Installation in a cored fiberglass hull (see page 3):

Hole saw for hull interior 60mm or 2-3/8"
Fiberglass cloth and resin
or Cylinder, wax, tape, and casting epoxy

Applications

• Recommended for fiberglass or metal hull only

• Never install a plastic thru-hull housing in a wood hull, since
swelling of the wood can possibly fracture the plastic.

• Low profile P371 recommended for cruising sailboats and
planing hull powerboats

• Flush P398 recommended for racing sailboats and high-speed
powerboats

• Minimum headroom required: 153mm (6")

• Accommodates hull thickness:
Minimum 6mm (1/4")
Maximum 25mm (1")

Mounting Location

CAUTION: Do not mount near water intake or discharge openings;

or behind strakes, fittings or hull irregularities that may disturb the
water flow.

CAUTION: Never mount the speed sensor directly ahead of a
depth transducer, since turbulence generated by the
paddlewheel’s rotation will adversely affect the transducer’s
performance, especially at high speeds. Mount side by side.

Turbulence-free water must flow under the paddlewheel at all
boat speeds. Choose an accessible spot inside the vessel. Allow
a minimum of 153mm (6") of headroom for the height of the
housing, tightening the nuts, and removing the insert.

paddlewheel
insert

housing

bore of housing

up 30mm (1-1/4")

outside wall below
lower O-ring

paddlewheel

paddlewheel
cavity

exterior flange of housing

washer
(some
installations)

sealant on flange
and side wall

paddlewheel
insert

cap nut

safety
wire

housing

hull nut

hull

arrow

Figure 1. Anti-fouling paint—low profile shown

Copyright © 2004 Airmar Technology Corp.

• Fin keel sailboats—Mount on or near the centerline and
forward of the fin keel 300 –600mm (1–2').

• Full keel sailboats—Mount amidships and away from the keel
at the point of minimum deadrise angle.

• Displacement hull powerboats—Locate amidships near the
centerline.

• Planing hull powerboats—Mount well aft to insure that the
sensor is in contact with the water at high speeds.

Anti-fouling Paint

Aquatic growth can accumulate rapidly on the sensor’s surface
reducing performance within weeks. Surfaces exposed to salt
water must be coated with anti-fouling paint. Use water-based
anti-fouling paint only. Never use ketone-based paint, since
ketones can attack many types of plastic possibly damaging the
sensor.

It is easier to apply anti-fouling paint before installing the sensor,
but allow sufficient drying time. Reapply paint every 6 months or
at the beginning of each boating season. Paint the following
surfaces (see Figure 1):

• Outside wall of the paddlewheel insert below the lower O-ring

• Paddlewheel cavity

• Paddlewheel

• Bore of the housing up 30mm (1-1/4")

• Exterior flange of the housing

• Blanking plug below the lower O-ring including the exposed end

Figure 2. Bedding and installing—low profile shown

Copyright © 2000 Airmar Technolog y Corp.

Bedding

Apply a 2mm (1/16") thick layer of marine sealant around the
flange of the housing that contacts the hull and up the sidewall of
the housing. The sealant must extend 6 mm (1/4") higher than the
combined thickness of the hull, any washer(s), and the hull nut
(see Figure 2). This will ensure there is sealant in the threads to
seal the hull and hold the hull nut securely in place.

Installing

1. From outside the hull, push the housing into the mounting hole
using a twisting motion to squeeze out excess sealant. Align the

arrow on the flange of the housing pointing forward toward the
bow (see Figure 2). If the sensor is not installed on the centerline

of the boat, angle the housing slightly toward the centerline to
align it with the water flow.

2. From inside the hull, slide any washer(s) onto the housing.

NOTE: Some installations do not have a washer.

Aluminum hull less than 6mm (1/4") thick—Use an additional
rubber, plastic, or fiberglass washer. Never use wood, since it
will swell, possibly fracturing the plastic housing. Never use
bronze, since electrolytic corrosion will occur.

3. Screw the hull nut in place, being sure the notch on the upper
rim of the housing is still positioned forward toward the bow. Do

Installation

Cored fiberglass hull—Follow separate instructions on page 3.

Hole Drilling

1. Drill a 3mm or 1/8" pilot hole from inside the hull. If there is a rib,
strut, or other hull irregularity near the selected mounting
location, drill from the outside.

2. Using a 51mm or 2" hole saw, cut a hole perpendicular to the
hull from outside the boat.
P398—This flush model requires countersinking the housing to
create a “seat” in the hull.

3. Sand and clean the area around the hole, inside and outside, to
ensure that the sealant will adhere properly to the hull. If there is
any petroleum residue inside the hull, remove it with either mild
household detergent or a weak solvent (alcohol) before sanding.
Metal hull—Remove all burrs with a file and sandpaper.

2

BOW ►

detail

large

O-ring

small

O-ring

Figure 3. Paddlewheel insert—no paddlewheel shown

Copyright © 2000 Airmar Technology Cor p.

key

notch