Improving my Simrad Sidescan – Part 2 (Initial Results and Issues)

So, where I left off on my last post, I had purchased a replacement transducer and installed it in the old mounting bracket. 

So, upon inspecting the new Simrad / Lowrance ActiveImaging 3 in 1 transducer, the first thing that was apparent was that it is significantly deeper than the StructureScanHD.  In other words, it sticks down farther from the mounting bracket.  When I mounted the new transducer I used the old bracket and this made the new unit stick down just a little below the bottom of the hull, maybe 1/2″.  In my haste to see what difference it would make, I took it out for a trial.  Turns out, that was a bad idea.  The force of the water hitting the transducer was enough to bend the metal bracket and twist it.  But, I was able to get some images to show that the new transducer is in fact a big improvement.

New transducer mounted on the old bracket. Note that it got bent after a sea trial!

Some initial screen shots after driving around at Edisto during a short family vacation:

First look: Suspended schools of menhaden.  Menhaden were flicking on the surface nearby, but not in this location.


First look: Dock pilings with potholes carved out around the bases.  Note the crisp shadows from the pilings.


Ah! Large redfish under a dock. Note the floater signature (thin vertical lines)

If you look closely at the above plots there are a few problems still…  

First, if you look at the center of the image.  This is where the transducer is.  Note that on the right you see a clear black zone, but on the left you see yellow lines where the water should be.  This is interference from the motor’s lower unit.  You could trim the motor up out of the way whenever you need sidescan but really, who’s gonna do that?  Not me.  The other very significant result of the lower unit interference is that the left side of the plot is almost useless.  You see almost no detail on that side, if you look at all the above plots.

It’s now clear that the transducer should be moved, both to mount it safely above the bottom of the hull for one, and also to hopefully allow a full 180 deg unobstructed view.  Looking around at my options, it appeared I could mount it near the center of the hull next to the drain plug and meet both requirements.  

New desired mounting location: Under the “step” and near the drain plug.

But, I wasn’t sure where exactly to mount it – and no one wants to drill more holes in their hull.  The next post will discuss how I solved these problems, and where I am at today.

A side note:  Ben made a point to say he purposely installs the transducer himself to make sure its done right.  I, like most people I guess, had the factory/dealership install it.  I’m honestly not sure who installed it but in hindsight, it was originally installed in a bad location for its purpose.  I would recommend anyone who reads this and is purchasing a new boat with side scan to either ask where its going to be mounted or do it yourself.  That is, if you want to get the most out of your unit! 

I’ll have the third part of this series updated in a few days…

One comment

  1. Roger Dunlap says:

    Thanks for going through this exercise with the presentation by Ben and particularly the follow up. I have a Simrad evo 3, and am getting some good information already, but also believe there are improvements to be made. Even though I have an expensive Airmar CHIRP through-hull transducer, its the transom mount Simrad ducer that gives a good reading on SONAR while running.

    While searching reefs, I switch back and forth, but expect to rely more on the scan in the future. Side-scan should help locate menhaden, but honestly, right now I do better watching for flicking on the surface. But I am thinking about getting the Active-imaging unit, having heard good reports on it. One final point, Ben was so right, my unit (one year old) is much better than my prior generation evo 2.

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