Operation Manual

ULTRASONIC SPEED SENSOR

There are two methods for preparing the hull to receive the housing:

1. Saturate layers of fibreglass cloth with a suitable resin and lay the cloth

inside the hole to seal and strengthen the core, adding layers until the

correct diameter is achieved.

2. Coat a cylinder of the correct diameter with wax and gently tap it into

the hole in the outer skin. Fill the gap between the cylinder and the

inner skin with casting epoxy. After the epoxy has set (refer to the

manufacturer’s instructions), remove the cylinder.

Clean and sand the area around the hole, inside and out, to ensure that the

sealant will adhere properly to the hull.

Remove the cap nut, sensor insert, hull nut and washer (refer to figure 4).

Apply a 2mm (1/16 inch) thick layer of marine sealant around the lip of the

housing. Apply a layer of sealant up the sidewalls of the housing to

approximately 6mm (1.4 inch) higher than the total thickness of the hull, washer

and hull nut. This will ensure that sufficient sealant will remain in the threads to

seal the hull and hold the nut securely in place.

From outside the hull, push the housing into the cut hole using a twisting

motion; this will squeeze out the excess sealant.

From inside the hull, slide the washer over the housing. Fit the hull nut and

tighten. If you are using a plastic housing, hand-tighten only on the hull nut, if

you are using a bronze unit, tighten the hull nut using slip-joint pliers.

After tightening, remove excess sealant on the outside of the hull to ensure

smooth water flow over the sensor.

Once the sealant has cured (refer to manufacture’s instructions), inspect the O-

ring seals on the sensor insert. Lubricate the seals using silicone grease or

petroleum jelly; slide the insert into the housing being sure to engage the key in

the notch, (a careful pushing twisting motion will ensure engagement). Fit the

cap nut and hand-tighten only.