Depth on sonar flashes. Wonder why.

[Navy Jr.]

Our Lowrance LMS 520C is a combo GPS/Sonar unit. Sometimes the depth reading will start to flash and continue that way for two minutes or more at the same reading while the boat is still moving (and the depth is changing). Happens when under main power or trolling. Eventually, it will snap out of it and show the actual reading again.

I've looked in the very detailed manual, but couldn't find anything about the flashing depth reading. Anyone here have an idea? Thanks. -Ken

 

[skargo]

Re: Depth on sonar flashes. Wonder why.

No idea what causes it, but it happens on occasion with my Raymarine A65. I noticed it happens at the same location as well.
I have a small, gauge size depth finder as a backup.

 

[dingbat]

Re: Depth on sonar flashes. Wonder why.

The transducer for one reason or another reason is having problems transmitting a signal, is having a problem hearing the return signal or the signal is being interfered with by something.

If it?s never worked properly then it?s a problem with the transducer installation. Transducers must have a clean flow of water over them. Air bubbles or turbulence off the hull will have a detrimental effect on their performance. If the unit worked properly and is just now starting to act up more than likely your transducer is going bad and needs replaced.

 

[Navy Jr.]

Re: Depth on sonar flashes. Wonder why.

Thanks for the replies. The unit and transducer are basically new (last year), and the flashing issue has been happening from the beginning. But it is an intermittent problem, so the I'll go with the explanation that the signal is somehow getting interfered with.

And there's probably nothing that can be done about it, except to look at the transducer and see if any weeds are hanging off it.

 

[skargo]

Re: Depth on sonar flashes. Wonder why.

As I said previously, my does it at a certain spot, a shallow area between a channel and some other deep water. I am thinking grasses are interfering in that spot.

 

[dingbat]

Re: Depth on sonar flashes. Wonder why.

As I said previously, my does it at a certain spot, a shallow area between a channel and some other deep water. I am thinking grasses are interfering in that spot.

You should be able to see thru grass on the bottom with not trouble.

Suspect it might be target masking in that area. Does it do it coming across the area in both direction? Are you running your sounder in Auto or manual mode?

See Page 5 of the attached

http://www.furunousa.com/Furuno/Doc/0/BLVCP5SLQMBK5ES16HH3K4MRB4/Transducer Handbook 2007 - web.pdf

 

[skargo]

Re: Depth on sonar flashes. Wonder why.

You should be able to see thru grass on the bottom with not trouble.

Suspect it might be target masking in that area. Does it do it coming across the area in both direction? Are you running your sounder in Auto or manual mode?

See Page 5 of the attached

http://www.furunousa.com/Furuno/Doc/0/BLVCP5SLQMBK5ES16HH3K4MRB4/Transducer Handbook 2007 - web.pdf

Interesting. that may be my issue. I have no idea what mode I am in. :redface:

 

[rjlipscomb]

Re: Depth on sonar flashes. Wonder why.

I have the same problem with my Lowrance. It's mounted in the hull below the engine. Performs okay when moving at low speeds. Once on plane, it flashes. Had the transducer replaced by the dealer and it still does the same thing. Sometimes flashes at minimal wake as well. Frustrating.

 

[4JawChuck]

Re: Depth on sonar flashes. Wonder why.

My Lowrance 527i (basically the same unit) doe the exact same thing, I have noticed it is not related to speed or angle/depth of the transducer as I have played with both...mine is less than a year old also. I have noticed it seems to do this in the same parts of the lake/river. The first few times it happened I killed the engine as I thought I was going real shallow and was hard on the motor trim to get the motor out of the water! When I look at the screen, the chart actually stops recording as though the unit froze and can't find the bottom.

I have experimented in the section of river where the unit seems to lose a signal and attribute it to fast moving turbulent water giving "noise" back to the unit, I still haven't figured out why it happens in water like a lake where there is little current and a lot less turbulence.

I have tried turning down the sensitivity and clutter rejection with little success, nothing seems to limit the "freezing". Obviously there is more at work here than I understand about sonar, I think more sophisticated sonar units have more side lobe rejection and are less susceptible to these events.

A sonar engineer is probably more skilled in decifering what is going on here and I hope one reads these forums and give us some insight into what is happening.

There is mention of a new beta software update in this thread that gives a shallow water option on our units, I have the latest software installed so I guess we have to wait until the software comes out of beta...I hate being a guinea pig.

http://bbcboards.zeroforum.com/zerothread?id=430627&postid=4215051

 

[dingbat]

Re: Depth on sonar flashes. Wonder why.

I have the same problem with my Lowrance. It's mounted in the hull below the engine. Performs okay when moving at low speeds. Once on plane, it flashes. Had the transducer replaced by the dealer and it still does the same thing. Sometimes flashes at minimal wake as well. Frustrating.

In hull mounting of a transducer can be tricky, sometimes almost impossible, depending on layup of your hull. You have to have good solid glass between the face of the transducer and the hull of the boat or all bets are off. Housing the transducer in an oil bath, or something similar that helps resonate the signal is especially effective on lower powered applications.

I've also seen a lot of people get into trouble when they over look hull obstructions and the angle the boat planes at speed. Mounting an inhull transducer aft of a strake or raw water intake is a very common problem. Mounting the transducer too far forward of the transom is also a common problem.

 

[skargo]

Re: Depth on sonar flashes. Wonder why.

One again, I have a Raymarine, but mine did it again today at the area I mentioned previously. It did it twice today, at areas where it goes from15' to 3-4' real quick, then it is fine.

Not sure it applies since it's not even the same brand.

 

[4JawChuck]

Re: Depth on sonar flashes. Wonder why.

Hmmm...just had a look at the Lowrance website and their is an update to resolve this problem on my unit! Same update for the 520 btw.

Have a look,

http://www.lowrance.com/en/Products/Marine/Full-Size-SonarGPS-Chartplotter-Combos/LMS-527C-DF-iGPS/Downloads/LMS-527C-DF-iGPS-Software-Update/

http://www.lowrance.com/en/Products/Marine/Full-Size-SonarGPS-Chartplotter-Combos/LMS-520C/Downloads/LMS-520C-Software-Update/


*UPDATE* I just loaded the software to my LR 527iGF but the web installer would not work with my MS Vista computer, I had to download the software manually and run it in Windows 2000 compatibility mode for the installer to work and load the SD card with the update. So far so good, there is new menus under the sonar options screen for fishing depths etc. Hopefully this resolves the problem I have experienced.

BTW make sure you go back into your unit after updating and reset all your custom options, after doing mine everything was reset to the default settings...my shallow alarm was disabled etc.

 

[Navy Jr.]

Re: Depth on sonar flashes. Wonder why.

The software on our unit is version 2.1. The update is to version 2.5, so for us an update is definitely needed. This is great! All I have to do is buy a card reader and do the update. Oh, and reset my customized options.

Thanks 4JawChuck! I see as of this posting you are only a cadet. I believe a promotion is in order. All the best. -Ken

 

[4JawChuck]

Re: Depth on sonar flashes. Wonder why.

Thanks, I don't mind being a cadet...less responsibility ya know!!

I just spent the last few days working on the boat and want to try the sonar out in the worst way...but of course its pouring rain and forecast is for all day.

I might just go out anyway, no kids will want to go for a ride today. Now where did I leave my goggles...

 

[Navy Jr.]

Re: Depth on sonar flashes. Wonder why.

Ok, I updated my Lowrance 520C operating system from version 2.1 to 2.5.

Went fishing this morning. Works much better. The most effective way is to go into Sonar Settings and change the new Fishing setting near the lower right corner. I set mine to match what I was doing ("Trolling Slow"), and it worked fine. But, it's a good idea to set it back to "General" (I think that's what it was called) before getting the boat up to speed under normal power or else you might get some bad depth readings along the way.

And, yes, you lose all of your customized settings. On mine, I somehow lost the memory of the GPS zoom, so have had to hit Zoom buttom a dozen or more times to get to the level of detail I want to see on my map every time I power up the unit. There's probably a setting to keep my zoom memory somewhere; still toying with it. -Ken

 

[Navy Jr.]

Re: Depth on sonar flashes. Wonder why.

Just in case anyone is interested or has been following this thread, there is indeed a menu setting that retains your zoom setting from the previous use of the GPS on the Lowrance 52x series (and probably other models, as well). Under the Map page, press menu and select Zoom. Press ENT and you're all set. -Ken

 

[4JawChuck]

Re: Depth on sonar flashes. Wonder why.

I also got a chance to work the unit this weekend, the shallow water setting is a lot more sensitive when your in the weeds but not so great when under power where the depth changes rapidly. I found the "general" fishing setting better for when your up on plane...no more annoying false alarms of low depth etc.

We got into some good fishing today although I wish it could be attributed to the sonar...sometimes it just pays to look at where the locals have parked themselves and drop your line.