Nexus 21 TH52 operation manual Installing the through hull fittings

English Sea Data Set TH52

2.3.2 Installing the through hull fittings

3 Installation

Cored fiberglass hull—Follow separate instructions on page 3.

Hole Drilling

Warning: Always wear safety goggles and a dust mask.

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 the hole from outside the hull. 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.

3.1Bedding

Apply a 2mm (1/16") thick layer of marine sealant around the lip of the housing that contacts the hull and up the sidewall of the housing. The sealant must extend 6mm (1/4") higher than the combined thickness of the hull, washer(s), and hull nut (see Figure 2). This will ensure there is sealant in the threads to seal the hull and to hold the hull nut securely in place.

3.2Installing

Caution: Never pull, carry, or hold the sensor by the cable as this may sever internal connections.

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 lip 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 rubber, fiberglass, or plastic washer. Never use bronze since electrolytic corrosion will occur. Never use wood since 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 lip are still positioned forward toward the bow. (If your plastic housing has wrenching flats, do not clamp tightly, possibly causing the housing to fracture.) Hand-tightenonly. Do not over tighten. Wood hull— Allow for the wood to swell.

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