Airmar ST800—Retractable with Valve - Manual (Page 2)

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 300–600mm (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-
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 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 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.
2
marine sealant on flange
Figure 2. Bedding and installing
cap nut
washer
hull
plastic housing
safety wire
housing
hull nut
insert
marine sealant
stainless steel housing metal housing
isolation
bushing
washer
in metal hull
and sidewall of housing and
(plastic)
marine sealant
cap nut
hull
safety
housing
insert
(plastic)
(metal)
hull nut
wire
(enlarged to show detail)
paddlewheel
Copyright © 2006 - 2010 Airmar Technology Corp.
on flange and sidewall on flange and sidewall
on isolation bushing
BOW ►
Figure 1. Anti-fouling paint
outside wall
bore of housing
exterior flange
O-ring
below lower
up 30mm (1-1/4")
of housing
insert
housing
paddlewheel
paddlewheel
paddlewheel
cavity
Copyright © 2006 Airmar Technology Corp.
in non-metal hull