POWER SOURCE FOR THE SONAR



In many cases, the trouble with the Sonar or Loran Receiver is caused by electrical noise from the boat's motor or an electrical device on the boat. The following questions explain how the Power cable should be wired, and other precautions to take to prevent electrical interference.

1. Is power cable wired directly to the battery or is it connected to the  fuse panel or ignition switch under the console?
   a) direct   b) fuse panel   c) ignition switch

The best answer is A. There is always less electrical noise present on the power lines when the positive and negative leads are connected directly to the battery (use 18 gauge wire). This is especially necessary for Loran-C units.

2. Is there any corrosion present on any of the splices or pins of the power cable?
     a) yes      b) no

The answer should be no. Corrosion on any of the connections can limit the amount of current the unit can use. This can reduce the units output power and its overall performance. The pins of the power connector, particularly the insides, are very susceptible to corrosion.

3. What type of splices is the power cable assembled with?
   a) soldered   b) crimped   c) clam shell

The best answer is A. Wires that are soldered together are as strong and protected from corrosion as if the wires had never been cut.
If the 'crimp on' splices are not crimped very well, the wires can develop a coating of oxidation.
The 'Clam Shell' type splices are the poorest type of splice. Since they leave the wires exposed where the metal clip cuts into them, they will eventually corrode.

4. Do you measure 12 volts at the power connector?
     a) yes      b) no

The answer should be yes. If you do not have 12 volts on the power and ground pins of the connector, follow the power cable back to the battery checking for 12 volts at each junction or splice.

5. Does the boat motor have resistor type spark plugs?
      a) yes      b) no
The best answer is yes. there will be less radiated noise from the wiring harness on motors that have resistor spark plugs installed.

6. Does the problem occur with the boat motor running and stopped?
     a) yes       b) no

If the answer is yes, the problem may be the transducer installation, a defective transducer, or a defective unit. If the answer is no and the problem does not occur when the motor is off, then there is probably electrical noise being generated by the motor. You should wire the power cable directly to the battery first, and if the problem persists, install resistor type spark plugs in the motor.

7. Does the problem occur with the boat sitting still and moving?
      a) yes       b) no

If the answer is yes, then the problem may be bad transducer installation, electrical interference, defective transducer, or defective unit. If the answer is no and the problem does not occur while the boat is not moving, then the transducer is cavitating or has turbulent water flowing around it when the boat is moving.

8. Does the problem occur only while the trolling motor is running?
      a) yes      b) no

If the answer is yes, then the trolling motor is probably generating electrical noise. For the most part, this problem only occurs with the Variable Speed Control - Battery Save feature type trolling motors. Try connecting the Sonar's Power cable directly to the main battery to see if this stops the interference.

Note: If possible. route the sonar's power cable on the other side
          of the boat from the trolling motor's power cable.

9. Are there any other electrical items (aerator, bilge. other sonar, etc.) on when problem occurs?
      a) yes       b) no

If the answer is yes, turn off all electrical equipment on the boat and try again. Then turn on each device one at a time to see which one is causing the interference. If the answer is no, then the problem may be the transducer installation, a defective transducer, or a defective unit.

TRANSDUCER INSTALLATION GUIDELINES

Please verify that your transducer installation complies with these guidelines.

1. The Two-Thirds Rule of Transducer Installation.

The Sonar's signal reflects off of anything that is of a different density than water. To the sonar, an air bubble flowing across the face of the transducer looks like a solid object. If the transducer has a lot of air bubbles flowing across its face due to turbulence or cavitation, the effect on the sonar is the same as if you were trying to see through a solid wall. For this reason, if you want the sonar to perform at all boat speeds the transducer has to be mounted where it will have a smooth flow of water across its face at all speeds

A good rule of thumb to follow for boats that have outboard motors or inboard/outboard motors is called the two-thirds rule. This simply states that the best water flow is available on the rear third and the center third of the boat's hull.

2. Water flow characteristics of different boat hulls.

A) Fiberglass hulls.
Areas of these hulls that have the most turbulence are along lifting  strakes, behind water intakes or props (on boats with inboard  motors), near trim tabs, and the area of the hull that is lifted out of the  water while the boat is on plane. Sonar will shoot through fiberglass very efficiently.

B) Aluminum hulls.
These hulls produce extremely turbulent water at the transom due to  the rivets they are made with. The transducer face should be at least  1' lower than the bottom of the transom. Welded hulls produce less turbulence, but it may still be necessary to mount the transducer 1'  below the transom. Sonar will not shoot through aluminum effectively.

C) Wooden hulls.
These hulls may produce turbulence around strakes or ribs, water intakes and props (on inboard motors), and portions of the hull that are lifted out of the water while the boat is on plane. Sonar will not shoot through wood at all.

D) Pontoons
Because of the open area between the pontoons, there are only two areas of smooth water flow. The first is beneath the pontoons, the second is immediately between and within the first four feet of the front of the pontoons. If you are going to mount the transducer where it will be beneath the pontoons, the sonar should work effectively at all speeds (there are several after-market transducer brackets that can do this).  If

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