I purchased my boat 5 years ago this past July, so I do not consider myself a “superior fisherman”, but I am able to share why I think fish finders are important equipment to have on a boat.
My boat came equipped with a Lowrence X-4 Pro fish finder, and being eager to get on the water I realized a few things:
Fish finders provide you with information about how shallow you can operate your specific boat without a hydraulic jack plate.
They also show you as you begin to move away from skinny water were the drop off begins as fish like to travel this ridge for a number of reasons
And, as has been mentioned you now know the water temperature
So, I started taking my boat to lakes that I have never been on and bigger than the last one, and that is when I realized that my Lowarance X-4 Pro located at the helm was not adequate for a specific issue:
The bigger the lake the more I could explore and the farther I went from where I launched my boat. When it came time to head back to the dock and daylight gave way to evening and I turned to head back to the dock, particularly on new and big lakes, I didn’t always recognize exactly where I was on the lake much let alone how to get back to the dock. So, I upgraded to a fish finder with a chart plotter and it came with down scan imaging; now I can go where I please and if concerned about where I am or how to get back to the dock I can have my fish finder plot a course back to my dock even in the dark.
Now with all this information at the helm I thought I was set except I don’t fish at the helm. I fish at the bow and that information on depth, water temperature, contour lines, boat orientation I no longer have access to unless I want to rearrange the unit at the helm, so I added a second and larger screen at the bow.
Now some of these guys and ladies have systems with side scan imaging and the ability to communicate waypoints and mark structure to multiple units, but they are expensive and may be suitable for your second upgrade.