Best Fish Finder for a muddy bottom

[brobille]

New to this board. Been bass fishing in my 6 acre lake behind my house for 25 years.

My kids got me a modern fish finder for my 70 birthday, HB Helix 7G3 MEGA DI.

I want to look at the structure in my lake that I put in there 25 years ago.

The HB was a disappointment. This was the best image I could get after trying every possible setting. After 25 years there is probably a foot of silt on the bottom. I took the Helix 7 back and tried the Helix 5 MEGA DI G2. Same results. The 7 had a trolling motor transducer mounted on the front of my 10 foot bass prowler. The Helix 5 had the longer transducer. Same quality images.

Question 1. Does that much silt caused to have such poor images?

Question 2. Is there a Fish Finder out there that can deal with silt

 

[Tennessee Boy]

Welcome to the forum.  The problem I see with the image you posted is the depth.  It’s hard to get a good image in such shallow water for many reasons.  There is a lot of noise known as surface clutter in the first few feet of water.  Fish finders filter this out to improve the image quality.  I suspect that these filters are removing all but the very strongest sonar returns from the image.  What’s left is what you’re seeing.   I’m not that familiar with your unit but there should be a way to turn off the filters and just show the raw returns.  What you will see with the filters turned off will probably be even harder to read.  Silt on the bottom absorbs more sonar energy and reflects less than rock or gravel.  Wood also doesn’t reflect well.  The fish finder is trying to make sense of a lot of noise along with a weaker than normal signal off the bottom and the brush on the bottom.  I think that’s the reason for the poor results.  Sorry but fish finders just aren’t that useful in less than 5 feet of water.  Is there any deeper water in the lake and if so have you tried it there?

[brobille]

Kicker, thanks for your reply. Yes, there is 17 feet of water also. I got the same type images for that water as well, but it also has 25 years of silt built up. Originally it was 19 feet at the over flow pipe. With my $100 units its now 17 feet so it may have two feet of silt. I'm afraid there isn't a unit made that can handle that type much silt

here is the 2D sonar along with the DI

[Team9nine]

Agree to a large degree with Tennessee Boy. The units aren’t the problem in the big scheme of things; neither is the silt.

 

In the first picture, it’s over-magnifying the image because of the small scale (0-6 ft). Everything will tend to look big and fuzzy, and usually the larger the screen, the worse the problem. Set the unit manually to 10 ft or greater to put things back into proper perspective. 

 

No issues with the second image either. 2d is nice and clean and reading well. Given your water temps, DI might be picking up a shallow thermocline, or possibly even a plankton migration. 

 

I’d consider taking the unit out of auto and manually adjust settings.  Don’t run depth shallower than 10 ft scale, and turn power down a little until you find a good clean reading. Might also consider  TB’s suggestion and turn off noise filters. On Humminbirds, you could also try running in Clear mode instead of Max mode.

[brobille]

Good advice Team9

thanks

Team9

This lake does develop a thermocline when the water reaches these temperature.

But nothing grows below the thermocline. I had an anchor out for some months and the rope was covered with algae (phytoplankton to be exact, the lake is fertilized). Below the thermocline the rope was like brand new.

Why would the image be fuzzy below the thermocline where there is no plankton there?

[Team9nine]

18 minutes ago, brobille said:

Why would the image be fuzzy below the thermocline where there is no plankton there?

 

The thermocline is a band of water, not just one exact depth. In that 2nd DI pic, you are only in about 7 ft of water or less. The “fuzz” starts at 5 ft. Very possible any plankton, etc. would get suspended in a 2 ft band. What we would need to see is what that DI pic looks like when you move out over 10 or 15 ft to be in a better position to interpret. See if there is a bottom to that “fuzz” that might suggest a thermocline.

 

Any  chance it rained recently before that pic was taken (1-3 days before), or even crazy strong winds?

[brobille]

No rain here for the past week, let me check to see if I have some deeper images

yganks Team9