Humminbird 957C manual Assembling the Transducer and Initial Mounting

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NOTE: If you have a flat-bottomed aluminum boat, some additional adjustment may be needed to accommodate the rivets on the bottom of the boat (i.e. the gap may need to be a little smaller than 1/8"). This will help you to avoid excessive turbulence at high speeds.

NOTE: If your propeller moves clockwise (in forward, as you're facing the stern of the boat from behind), mount the transducer on the starboard side, and align the bottom right corner of the mounting bracket with the bottom of the boat. If your propeller moves counter-clockwise (in forward, as you're facing the stern of the boat from behind), mount the transducer on the port side, and align the bottom left corner of the mounting bracket with the bottom of the boat.

3. Assembling the Transducer and Initial Mounting

In this procedure, you will assemble the transducer using the hardware provided, then mount it and make adjustments to its position without locking it in place.

NOTE: You will initially assemble the transducer and the pivot arm by matching the two ratchets to a numbered position on the transducer knuckle. Further adjustments may be necessary.

1a. If you already know your transom angle, refer to the chart below for the initial position to use to set the ratchets. If your transom is

3.Continue to hold the bracket on the transom of the boat, and use a pencil or marker to mark where to drill the two mounting holes. Mark the drill holes near the top of each slot, making sure that your mark is centered in the slot.

Using the Mounting Bracket to Mark the Initial Drill Holes

Third Hole

angled at 14 degrees (a common transom angle for many boats) use position 1 for the ratchets. In either case, go to step 2.

or...

Bead Alignment	1	4	2		5		3		1		4			2	5		3			1
Number
Transom Angle (°)		1 2	3	4 5	6	7 8	9	10 11	12	13 14	15	16 17 18	19	20 21		22 23	24	25 26 27	28	29 30
	-2 -1 0

NOTE: The third hole should not be drilled until the angle and height of the transducer is finalized, which you will not do until a later procedure.

4.Make sure that the drill bit is perpendicular to the actual surface of the transom, NOT parallel to the ground, before you drill. Using a 5/32” bit, drill the two holes only to a depth of approximately 1”.

Mark Initial	Fourth Hole
Drill Holes

Measured Distance (x)	0.0 cm	1.1cm	2.5 cm	4.3 cm	5.9 cm	7.6 cm	9.3cm	11.1cm	12.9cm	14.9cm	16.9cm
	0“	1/2“	1“	1 5/8“	2 3/8“	3“	3 5/8“	4 3/8“	5“	5 7/8“	6 5/8“

1b. If you do not know your transom angle, measure it using a plumb line (weighted nylon string or monofilament line) exactly 12 inches long. Hold the top of the plumb line against the top of the transom with your finger, and wait until the line hangs straight down. Using a ruler, measure the distance from the bottom of the plumb line to the back of the transom, then use the chart.

NOTE: On fiberglass hulls, it is best to use progressively larger drill bits to reduce the chance of chipping or flaking the outer coating.

NOTE: It is important to take your measurement in the figure showing Measuring the Transom Angle, from exactly 12 inches down from the top of the transom.

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