False fish readings
False fish readings are commonly caused by electrical interference such as alternator noise, and by air bubbles flowing across transducer.
For starters make sure your fishfinder is on an independent circuit and not on one powered by your ignition switch. In other words, you should be able to turn your fishfinder on, even though the engine is turned off. Ideally the fishfinder should be wired directly to the battery with an in line fuse.
Try running the boat at a speed slightly higher than trolling speed, then kill the engine, as the boat slows down to trolling speed do you still see false echos? If yes then the problem probably lies with how the transducer is mounted, or where it is located on the hull.
If you don't see the false echos when the engine is off, it may be necessary to reroute the transducer cable to keep it away from the boat's ignition wires. You can get transducer extension cables if necessary. Also there are filters that you can buy that suppress alternator noise buy attaching between the battery and the engine.
Another common cause of false echos from electrical interference is a transducer cable that has been cut and spliced.
I hope this information helps. Please reply if you have any questions about my response.
Feb 25, 2008 |