Airmar HT200 User Manual
INSTALLATION INSTRUCTIONSOWNER’S GUIDE &
Thru-Hull, Retractable with Valve
Temperature or Speed Temp Sensor
Models: HT200, ST850
U.S. Patents: 7,110,908; 7,352,171. UK 2 409 527
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.
17-422-01 rev. 04 02/01/11
WARNING: The valve is not a watertight seal! Always
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.
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 install a metal housing in a vessel
with a positive ground system.
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.
CAUTION: A stainless steel housing must be isolated
from a metal hull to prevent electrolytic corrosion.
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. Check for the approximate air
temperature. If it has a paddlewheel, spin it and check for a speed
reading. If there is no reading(s) or it is 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___________
HT200
plastic
low profile
P17 housing
ST850
plastic
low profile
P17 housing
Applications
• Plastic housing recommended for fiberglass or metal hulls only.
Never install a plastic housing in a wood hull since swelling of the wood
may overstress the plastic causing a fracture.
• Bronze housing recommended for fiberglass or wood hull only.
Never mount a bronze housing in a metal 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)
Countersink tool (installing a flush housing)
Sandpaper
Mild household detergent or weak solvent (such as alcohol)
File (installation in a metal hull)
Marine sealant (suitable for below waterline)
Slip-joint pliers (installing a metal housing)
Grommet(s) (some installations)
Cable ties
Installation in a cored fiberglass hull (see page 4)
Hole saw for hull interior 60mm or 2-3/8"
Fiberglass cloth and resin
or Cylinder, wax, tape, and casting epoxy
57mm or 2-1/4" (stainless steel housing in a metal hull)
Mounting Location
CAUTION: Do not mount in an area of turbulence or bubbles near water intake
or discharge openings; or behind strakes, fittings or hull irregularities.
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.
Choose an accessible spot inside the vessel. Allow a minimum of 280 mm
(11") of headroom for the height of the housing, tightening the nuts, and
removing the insert.
HT200—The sensor must be in contact with the water at all times.
ST850—Turbulence-free water must flow over the paddlewheel at all boat
speeds.
• 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.
paddlewheel
insert
outside wall
below
lower O-ring
paddlewheel
paddlewheel
cavity
bore of
valve assembly
up 30mm (1-1/4")
housing
exterior flange
of housing and
valve assembly
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, and hull nut. This will ensure there is sealant
in the threads to seal the hull and to hold the hull nut securely in place.
Stainless steel housing in a metal hull—The stainless steel housing
must be isolated from the metal hull to prevent electrolytic corrosion. 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.
Figure 1. Anti-fouling paint (ST850 low-profile housing shown)
Copyright © 2005 Airmar Technolog y Corp.
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 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):
• Bore of the valve assembly up 30mm (1-1/4")
• Exterior flange of the housing and valve assembly
• Blanking plug below the lower O-ring including the exposed end
• Temperature insert below the lower O-ring including the exposed end
• Paddlewheel insert:
--Outside wall below the lower O-ring
--Paddlewheel cavity
--Paddlewheel
Installation
Hole Drilling
Cored fiberglass hull—Follow separate instructions on page 4.
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 boat.
Flush housing—Use a countersink tool 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.
Installing
CAUTION: If your sensor came with a connector, do not remove it to ease
cable routing. If the cable must be cut and spliced, use Airmar’s splashproof Junction Box No. 33-035 and follow the instructions provided.
Removing the waterproof connector or cutting the cable, except when
using a watertight junction box, will void the sensor’s warranty.
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.
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. If necessary, sand the
isolation bushing until the washer rests against the hull.
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.
Metal 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 hull nut.
4. Remove any excess marine sealant on the outside of the hull to ensure
smooth water flow over the sensor.
5. After the marine sealant cures, inspect the O-rings on the valve
assembly (replace if necessary) and lubricate them with the silicone
lubricant supplied (see Figure 3). The O-rings must be intact and well
lubricated to make a watertight seal.
6. Slide the valve assembly into the housing. Seat it into place with a
pushing twisting motion until the key fits into the notch. Screw the CAP
nut in place and hand tighten only. Do not over tighten.
plastic housing stainless steel housing in metal hull
P17 shown B17 shown
BOW ►
marine sealant
on flange and sidewall
of housing
metal housing in non-metal hull
Figure 2. Bedding and installing
Copyright © 2005 - 2010 Airmar Technol ogy Corp.
pull ring
paddlewheel insert
insert nut
safety wire
cap nut
emergency plug
hull nut
washer
hull
(ST850 shown)
SS577 shown
marine sealant on flange
and isolation bushing where it contacts hull
and sidewall of housing
2
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