Airmar ST800 Owner's Manual And Installation Instructions - page 2
CAUTION: Do not mount the sensor in line with or 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
Surfaces exposed to salt water must be coated with anti-fouling
paint. Use water-based anti-fouling paint only. Never use ketone-
based paint, because 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 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 a 51mm or 2" hole saw, cut a hole perpendicular to the
hull from outside the boat.
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 will contact 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 marine 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 marine 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
because electrolytic corrosion will occur. Never use wood
because it will swell, possibly fracturing the plastic housing.
3. Screw the hull nut in place being sure the notch on the upper
rim of the housing and the corresponding arrow on the flange
are still positioned forward toward the bow.
Plastic housing—Do not clamp tightly on the wrenching flats,
possibly causing the housing to fracture.
Plastic hull nut—Hand tighten only. Do not over tighten.
Bronze hull nut—Tighten with slip-joint pliers.
Cored fiberglass hull—Do not over tighten, crushing the hull.
Wood hull—Allow the wood to swell before tightening the nut.
4. Remove any excess marine sealant on the outside of the hull to
ensure smooth water flow under the sensor.
5. The O-rings must be intact and well lubricated to make a
watertight seal. After the marine sealant cures, inspect the
O-rings on the insert (replace if necessary) and lubricate them
with the silicone lubricant supplied.
2
Figure 2. Bedding and installing
cap nut
washer
hull
safety wire
housing
hull nut
insert
marine sealant on flange
bronze housing in non-metal hull
(plastic)
marine sealant on flange
paddlewheel
and sidewall of housing
and sidewall of housing
BOW ►
Figure 1. Anti-fouling paint
outside wall
bore up 30mm (1-1/4")
exterior flange
O-ring
below lower
insert
housing
paddlewheel
paddlewheel
paddlewheel
cavity
Copyright © 2006 Airmar Technology Corp.
B120
plastic housing
P120
Copyright® 2006 - 2015 Airmar Technology Corp.