Airmar ST800 User Manual

INSTALLATION INSTRUCTIONSOWNER’S GUIDE &

Thru-Hull, Retractable with Valve

Speed & Temperature Sensor

Model ST800

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
use the insert or blanking plug secured with the safety

17-396-01 rev. 04 04/04/11

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
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.

WARNING: Stainless steel housing in a metal hull—
Be sure the washer contacts the hull. Do not tighten
the hull nut with the washer against the isolation
bushing, as the housing will not be firmly installed.

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

CAUTION: Never install a metal housing on a vessel
with a positive ground system.

CAUTION: A stainless steel housing must be isolated
from a metal hull to prevent electrolytic corrosion. Use
the isolation busing supplied.

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

CAUTION: The arrow on the top of the insert must
point forward toward the bow.

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.

Pretest

Connect the sensor to the instrument and spin the paddlewheel. Check for
a speed reading and the approximate air temperature. If there are no
readings or they are inaccurate, check the connections and try again. If
there is still a problem, return the product to the place of purchase.

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

Part No._________________Date___________

ST800

plastic
low profile
P120 housing

Applications

• Plastic housing recommended for fiberglass or metal hull only.

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

• Bronze housing recommended for fiberglass or wood hull.

Never mount a bronze housing in an aluminum hull because
electrolytic corrosion will occur.

• Stainless steel housing compatible with all hull materials.
Recommended for aluminum hulls to prevent electrolytic corrosion

provided the stainless steel housing is isolated from the metal hull.

Tools & Materials

Safety goggles
Dust mask
Water-based anti-fouling paint (mandatory in salt water)
Electric drill with 10mm (3/8") or larger chuck capacity
Drill bit: 3mm or 1/8"
Hole saw: 51mm or 2" (plastic or metal housing in non-metal hull)

57mm or 2-1/4" (stainless steel housing in metal hull)

Sandpaper
Mild household detergent or weak solvent (such as alcohol)
File (installation in a metal hull)
Marine sealant (suitable for below waterline)
Additional washer [for aluminum hull less than 6mm (1/4") thick]
Slip-joint pliers (installing a metal housing)
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

Mounting Location

Turbulence-free water must flow over the paddlewheel at all boat
speeds. Choose an accessible spot inside the vessel. Allow a
minimum of 280mm (11") of headroom for the height of the
housing, tightening the nuts, and removing the insert.

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

CAUTION: Do not mount the sensor in an area of turbulence or
bubbles; near water intake or discharge openings; behind strakes,
fittings, or hull irregularities that will disturb the water flow.

• Displacement hull powerboats—Locate amidships near the
centerline.

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

• Fin keel sailboats—Mount on or near the centerline and
forward of the fin keel 300–6 00mm (1– 2').

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

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 plastics possibly damaging the sensor.

It is easier to apply anti-

paddlewheel
insert

outside wall
below lower
O-ring

paddlewheel

paddlewheel
cavity

housing

exterior flange

bore of housing
up 30mm (1-1/4")

Figure 1. Anti-fouling paint

Copyright © 2006 Airmar Technol ogy Corp.

of housing

fouling paint before
installation, 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

• Paddlewheel cavity

• 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

Installation

Hole Drilling

Cored fiberglass hull—Follow separate instructions on page 3.

1. Drill a 3 mm 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 the appropriate size hole saw, cut a hole perpendicular to
the hull from outside the hull.

3. Sand and clean the area around the hole, inside and outside, to
ensure that the marine 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.

Bedding

CAUTION: Be sure the surfaces to be bedded are clean and dry.

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 (see Figure 2). The sealant must extend 6mm (1/4")

higher than the combined thickness of the hull, washer(s), and
hull nut. This will ensure there is sealant in the threads to seal the

hull and hold the hull nut securely in place.
Stainless steel housing in a metal hull—To prevent electrolytic

corrosion, the stainless steel housing must be isolated from the
metal hull. Slide the isolation bushing onto the housing. Apply
additional sealant to the surfaces of the bushing that will contact
the hull, filling any cavities in and around the bushing.

Installing

1. From outside the hull, push the housing into the mounting hole
using a twisting motion to squeeze out excess sealant (see
Figure 2). Align the arrow on the flange of the housing to point
forward toward the bow. If the sensor is not installed on the
centerline, angle the housing slightly toward the centerline to
align it with the water flow.

2. From inside the hull, slide the washer onto the housing.
Aluminum hull less than 6mm (1/4") thick—Use an additional

rubbery, fiberglass, or plastic washer. Never use bronze since
electrolytic corrosion will occur. Never use wood since it will
swell, possibly fracturing the plastic housing.

plastic housing

marine sealant

on flange and sidewall

paddlewheel

insert

cap nut

(plastic)

housing

safety wire

hull nut

washer

hull

in non-metal hull

marine sealant

on flange and sidewall

BOW ►

stainless steel housingmetal housing

in metal hull

(enlarged to show detail)

marine sealant on flange

and sidewall of housing and

on isolation bushing

insert

cap nut

(plastic)

safety
wire

housing

hull nut
washer

(metal)

hull

isolation
bushing

Figure 2. Bedding and installing

Copyright © 2006 - 2010 Airmar Tech nology Corp.

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