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Author Topic:   Depthsounder Can't Read Bottom
bfish25 posted 07-26-2010 04:47 PM ET (US)   Profile for bfish25   Send Email to bfish25  
Hello. I am new to this site and a first time boater. I have a Garmin 498. The display was flashing because [the depthsounder] couldn't read the bottom. This was happening most of the day. Tell me why this happens. Is there a way to fix it when it happens? I noticed the water was brown this weekend; I don't know if that has anything to do with [the depthsounder losing the bottom]. Thank you for any and all advice you can give me. Good luck the rest of the season.
Buckda posted 07-26-2010 04:53 PM ET (US)     Profile for Buckda  Send Email to Buckda     
It could be a lot of things, including where and how you have the transducer mounted to your hull.

Did this setup work well before, and this is a developed problem, or is it a new installation, or a new-to-you boat?

Make sure the transducer is in "clean" water - no strakes or chines ahead of it on the hull. Aerated, turbulent water can sometimes really confuse the sounder and create a faint/flashing display.

bfish25 posted 07-26-2010 05:03 PM ET (US)     Profile for bfish25  Send Email to bfish25     
Hi, I am new to boating just bought my first one and trying to learn a whole lot of stuff. It was working at certain parts of the day. It was a weekend there were a ton of boats out making some serious wakes all over couldnt be avoided plus the water looked brown. The water temp was 81-83. Most of the day all it did was flash and wouldnt work again.
Buckda posted 07-26-2010 05:11 PM ET (US)     Profile for Buckda  Send Email to Buckda     
"Brown" water typically doesn't cause too many problems for transducers/sounders - and nor does choppy conditions (unless it works find when you're trolling or at anchor and has all kinds of problems at speed).

If it works when anchored/at your slip, then we can zero in on a possible transducer placement problem. If it doesn't work anyway, then it could be an installation problem of the unit or a problem with the unit (actual "head" unit, or transducer unit) itself. If you can find a friend who has a similar Garmin unit, you can swap head units and plug your head unit to his transducer to find out if it is your transducer or your head unit.

That would be my second step.

The first step for me would be to disconnect all the wiring/cables and REINSTALL it - making sure you have a solid, FUSED electrical connection to power and to ground.

meridian posted 07-26-2010 05:37 PM ET (US)     Profile for meridian  Send Email to meridian     
I have the same unit. A few weeks ago I noticed the same thing you did. I found my transducer had rotated up one notch. I angled it back down and tightened the screw. Now runs fine.
bfish25 posted 07-27-2010 09:16 AM ET (US)     Profile for bfish25  Send Email to bfish25     
Thanks guys I appreciate the advice. Will try it this weekend.
jimh posted 07-28-2010 12:31 AM ET (US)     Profile for jimh  Send Email to jimh     
If a depthsounder is not reading a bottom echo, the most likely cause is a poor SONAR transducer installation. The position of the SONAR transducer is very important. Sometimes a change in the depth of the immersion of the SONAR transducer into the water by just a quarter-inch will make a significant difference in the performance, particularly when the boat is moving. I imagine your boat has a transom mounted SONAR transducer. See my advice in

jimh posted 07-28-2010 12:32 AM ET (US)     Profile for jimh  Send Email to jimh     
Also see

bfish25 posted 07-28-2010 11:12 AM ET (US)     Profile for bfish25  Send Email to bfish25     
Yes it has a transom mounted transducer. The boat is in the water right now do i need a mechanic to do this or is this something i could look at? I appreciate all the advice thank you.
jimh posted 07-29-2010 01:07 AM ET (US)     Profile for jimh  Send Email to jimh     
It is typical that the mounting bracket for a SONAR transducer to mount on a transom will have an arrangement of slotted holes so that the position of the transducer on the transom can be adjusted slightly without having to drill new mounting holes. If you can operate a screwdriver you can probably adjust the position of the SONAR transducer on the transom.
Plotman posted 07-29-2010 11:44 AM ET (US)     Profile for Plotman  Send Email to Plotman     
There is a bolt or screw that goes from side to side that attaches the actual transducer to the bracket that is screwed to the hull.

If you loosen this bolt, you will find that you can rotate the transducer up and down. There are teeth that line up to hold the orientation fixed when the bolt is tightened. I would suggest you do this and move the transducer down one or two notches and see where you are.

You want the transducer to be parallel with the bottom of the boat, or even a touch nose high.

I could not imagine using a mechanic to do this.

davej14 posted 08-03-2010 09:48 AM ET (US)     Profile for davej14  Send Email to davej14     
If you decide to loosen the screws that attach the sounder to the transom for adjustment you should re apply marine sealer rated for below the water line to the screws. I would do this after "dialing in" the position. Once you have it where you want, take out one of the screws completely, clean up the threads, apply the sealer and re install. Repeat for the other screw.

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