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False fish readings

I have a lowrance x87 fish finder at slow speeds in shallow water it reads fish when the motor is at trolling speed. What can I do to stop this?

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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.

Posted on Feb 26, 2008

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When at speed i tend to lose sight of the bottom it becomes very broken. Also the depth reading takes a while to record depth.


What you are experiencing sounds like air bubbles crossing the face of the transducer. If you have a transom mount transducer check the face of the transducer. Make sure that it is clean. Also make sure the front of the transducer is a tiny bit lower than the back. The digital readout on the screen will only happen when you have a strong signal of the bottom.

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Transducer loses bottom at any type of speed greater than trolling. Worked fine last year with all the same setttings. All I can think of is , maybe the battery is low. The boat just came out of storage...


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Are you looking for the fish arches?
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There is an OK guide to understanding what you see on the sonar screen at the link below. It if pretty technical but parts of it may help you out.

http://primus.lowrance.com/support/resultDisplay.do?gotoLink=5&docType=1000&contextId=351%3A5.47%2C11918.11930%2C22.47&clusterName=ClusterPublic&lang=english&docset=%2FDocuments%2FSonar&contentId=9de88fa2-0b60-4b44-a470-29ee14767b3e&responseId=135ccbe2cfd4f608%3A1fe88d%3A122773df7e0%3A7c2&groupId=4&answerGroup=1&score=981&page=http%3A%2F%2Fprimus.lowrance.com%2Ficr%2FSonar%2FChart+Tutorial.htm&result=0&excerpt=Chart+Tutorial+Deciphering+Sonar+Charts.&question=chart+tutorial&resultType=5000#Goto5

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