Operation, Maintenance, and Repair

How the Valve Works

The sensor incorporates a self-closing valve which minimizes the ﬂow of water into the vessel when the ultrasonic insert is removed. The curved ﬂap valve is activated by both a spring and water pressure. Water pushes the ﬂap valve upward to block the opening, so there is no gush of water into the boat.

WARNING: THE VALVE IS NOT A WATERTIGHT SEAL!

Always install the ultrasonic insert or the blanking plug secured with the safety wire for a watertight seal.

Using the Blanking Plug

To protect the ultrasonic insert, use the blanking plug when:

•The boat will be kept in salt water for more than a week.

•The boat will be removed from the water.

•Aquatic growth build-up is suspected due to inaccurate readings from the instrument.

Warning: The O-rings must be intact and well lubricated to make a watertight seal.

1.Inspect the O-rings (replace if necessary) and lubricate them with the silicone lubricant supplied or petroleum jelly (Vaseline®) (see Figure 5).

2.Assemble the blanking plug. Place the cap nut on top of the plug and attach the pull ring to capture the cap nut.

3.Remove the ultrasonic insert from the housing by removing the safety wire from the cap nut (see Figure 3).

4.Unscrew the cap nut to jack the insert out of the housing. This will remove the cap nut and insert as a single unit.

Warning: Always attach the safety wire to prevent the insert from backing out in the unlikely event that the cap nut fails or is screwed on incorrectly.

5.Slide the blanking plug into the housing with the arrow pointing forward toward the bow (see Figure 5). Seat it into place with a twisting motion until the key ﬁts into the notch. Screw the cap nut in place and hand-tightenonly. Do not over-tighten. Reattach the safety wire (see Figure 3).

Servicing the Ultrasonic Insert

Caution: The active face of the ultrasonic insert is very fragile and easily damaged. Do not scratch, gouge, or sand it with coarse sandpaper.

Aquatic growth will seriously affect the ultrasonic insert’s performance. Clean the active face with a dull putty knife being careful to avoid scratching the surface (see Figure 5). If fouling is severe, lightly wet sand the surface with ﬁne grade (#320) wet/dry paper.

O-rings must be free of abrasions and cuts to ensure a watertight seal. Install the large O-ring near the cap nut, the medium O-ring below it, and the small O-ring near the active face. The three remaining O-rings are placed in similar positions on the blanking plug (see Figure 5).

Servicing the Valve Assembly

Should the valve fail, remove it for servicing. A replacement O-ring and Valve Kit 33-450-01 is available.

1.On the blanking plug, inspect (replace if necessary) and lubricate the O-rings with silicone lubricant or petroleum jelly (Vaseline®).

	top view of
	ultrasonic	blanking
	insert	blanking
	insert	plug
		plug
		large O-ring
	ultrasonic	medium O-ring
	insert	medium O-ring
	insert
		small O-ring
		active face
	valve	snap ring
	assembly	valve assembly with
		flap valve, spring,
		and retainer pin
		notch

housinghousing

BOW •

Figure 5. Servicing

2.Remove the ultrasonic insert from the housing (see Figure 3).

3.Remove the snap ring from the valve assembly using a screwdriver to pry the end of the ring free (see Figure 5).

4.Slide the valve assembly upward and out of the housing slowly. Note: The ﬂap valve retainer pin is a loose slip-ﬁt and may slide out when the assembly is removed.

5.Slide the blanking plug (or ultrasonic insert) into the housing with the arrow on the top pointing forward toward the bow. Seat the plug into place with a twisting motion until the key ﬁts into the notch. Screw the cap nut in place and hand-tightenonly. Do not over-tighten. Reattach the safety wire (see Figure 3).

6.Clean, repair, or replace the valve assembly so the ﬂap valve moves freely and seats against the valve housing (see Figure 5).

7.Remove the blanking plug. Slide the valve assembly into the housing with the ﬂap valve pointing downward. Insert the snap ring being certain that it locks into the groove in the housing wall.

Warning: Always attach the safety wire to prevent the insert from backing out in the unlikely event that the cap nut fails or is screwed on incorrectly.

8.Slide the ultrasonic insert into the housing with the arrow on the top pointing forward toward the bow. Screw the cap nut until there is resistance.Seat the ultrasonic insert into place by rotating it until the key clicks into the notch. Continue to screw the cap nut into place hand-tighteningonly. Do not over- tighten. Re-attach the safety wire (see Figure 3).