.I’ve learned over the years that most anglers make a lot of fish finder mistakes when looking for fish. I get tons of questions from people both on social media and on my guide boat about fish finders and have a ton of anglers that come to me to better learn how to use and read their sonar. Several years ago I started to notice a pattern. Almost every angler that contacted me would make the same fish finder mistakes. That’s why I put this resource together.
I finally got around to putting together this article and video covering these top 5 fish finder mistakes that most anglers make. If you’ll pay close attention to the information covered in this video and make the suggested changes you’ll unleash the true power of your down imaging, side imaging, and 2D sonar and you’ll be a better angler because you’ll find and catch more fish!
These fish finder tips aren’t just for catfish anglers as these rules apply to any species of fish!
I use Humminbird fish finders but the same principles apply to Lowrance and other brands.
Fish Finder Installation Problems
Fish finders that have not been installed correctly are a constant battle. This can range from power cycle problems (shutting down), interference on the screen so you don’t get good images, and even loss of image clarity from voltage issues. Don’t assume just because a marine dealer has installed your electronics that they are installed correctly.
I prefer to wire sonar fish finders directly to the battery with an inline fuse bypassing switch panels, fuse blocks, and other possible sources of problems and interference (just one of many fish finder installation tips). Making sure you use the correct gauge marine grade wire is also critical to avoid fish finder power cycle and shutting down issues.
It’s equally important (if not more important) to get good images on your fish finder to have a good clean transducer installation. The transducer must be installed at the right location on the back of the boat and at the right height (not too low and not too high). Sometimes this means moving a transducer install location a few times (which is why you always use a poly mounting board).
If you’re shooting a rooster tail or having other issues, this shows you’ve got a transducer installation issue and it needs to be moved. A poorly installed transducer can also cause major performance problems with boats as well causing anything from listing to impacts on speed!
Having a transducer properly leveled is critical as well. A transducer tilted a few degrees forward or backward will have dramatic impacts on image quality and leveling a fish finder transducer is so simple. You can get all the details on how to level your fish finder transducer here.
If your fish finder is already installed then there are some easy fish finder troubleshooting steps here.
Scan Speed (Slow and Straight)
2D, Down Imaging, and Side Imaging are designed to work from a moving boat, they’re not made to work sitting still (or barely moving). It’s possible to adjust the fish finder speed and settings to have a general idea of what’s below the boat but you’re not going to get detailed images.
You need to be driving to properly scan for fish and with the chart speed properly set. A good general rule is to have the chart speed set equal to or slightly higher than the boat speed. Scanning at 1 to 3 miles an hour is going to provide the best results and the most detailed images. If you’re scanning for fish at 3 miles per hour as a boat speed then set your chart speed to 3 or 4 miles per hour to get the best images. Sitting still or driving fast doesn’t typically give you the detailed images needed to find fish unless you’re using a tool like Humminbird 360 or Live Imaging.
If your chart speed is too slow or the boat isn’t moving it will make fish look bigger than they really are! This is one of the biggest fish finder mistakes when it comes to estimating fish size.
If you drive too fast (or have the scroll speed too fast) it will make the fish look smaller than they actually are. Additionally, if you’re driving too slow (or sitting still) it will stretch the images out and make the fish look bigger than they actually are.
In addition to making sure you’re scanning at the right speeds with the right chart speed on your fish finder, you need to make sure you scan in a straight line (as much as possible). Slow and straight will produce the best images.
Fish Finder Sonar Cones (More Detail Isn’t Always Better)
Not understanding sonar cones or not using the correct sonar type or frequency is a common issue.
Most modern fish finders come with 83/200 on 2D sonar and 455 and 800 for side imaging and down imaging. With Humminbird fish finders, they also have MEGA imaging (1.2 MHZ). Higher frequency sonar provides more details but is also a much smaller cone. The higher frequency the smaller the sonar cone will be.
It doesn’t matter if you’re using 2D sonar, down imaging, or side imaging. Not understanding sonar cones, how they work, and when and why to adjust them is costing you fish.
Let’s use 2D sonar as an example. In 20 feet of water, a 200 kHz sonar is looking at a cone (circle) that’s about 7 feet around on the bottom. The 83 kHz sonar is much wider. This shows a circle about 23 feet around.
If you’re scanning 20 feet of water viewing a 7-foot circle on the bottom do you think you’ll see much fish?
No, absolutely not.
That’s why most anglers run their fish finders in 83/200. This alternates frequencies giving you the best of both worlds, details, and coverage.
Down imaging and side imaging are the same. The higher the frequency the smaller the cone angle. 455 kHz shoots a wider cone than 800 kHz. When you jump to MEGA (1.2 MHZ) you get an even smaller cone.
Lower frequencies are better for searching for structure, cover, and fish. Once you find them and identify a location, get in closer and use a high frequency for getting more details. If you want to take pretty pictures for the internet then high frequencies are great. For finding fish or “searching” you’re often much better off with lower frequencies.
Fish Finder Color Palettes
Most fish finders come set with blue as the standard color palette for down imaging and side imaging. Many anglers leave these settings as default. Everyone’s eyes are different. Making changes to color pallets can often make a huge difference in the ability to find and catch fish!
I have a really hard time seeing fish and details with the blue color palettes. I prefer the Amber 2 color palette on Humminbird units most of the time. There are times when certain conditions dictate a change and I’ll switch back to blue.
Experiment with different color pallets on side and down imaging. Try different settings at different times of the year and in different conditions and see what works best for you.
Sensitivity and Contrast
This is the single biggest fish finder mistake anglers make. Modern fish finders provide really good images right out of the box (assuming they’re installed correctly). Adjustments are constantly needed as you’re fishing though. When water conditions change, you have to make adjustments to contrast and sensitivity.
Many modern fish finders include a dynamic contrast option. This adjusts these settings automagically (or you can manually adjust contrast and sensitivity). I prefer to adjust these settings manually. Contrast and sensitivity are two settings that have to constantly be adjusted as you’re fishing. Every time you change depths, water conditions, or sonar cones, adjust the contrast and sensitivity as needed.
These are settings that should constantly be adjusted, I’d guess I change contrast and sensitivity hundreds of times a day. If your sensitivity is too high (also called a “hot image”) detail will be washed out. If your sensitivity is too low, the image will be too dark.
When you change depths, bottom hardness, etc, you’ll have to adjust contrast and sensitivity. Sometimes these are minor adjustments and sometimes they’re BIG adjustments.
Here’s the video!
Change Settings Now and OFTEN
Next time you’re on the water pay close attention to these settings. Make adjustments based on how and where you’re scanning for fish. Grab some rods and start fishing and you’ll be surprised how quickly you’ll become a better angler.