Couple suggestions.
Ditch that main switch. You don't need it. Instead, install a keyed battery disconnect, so you can leave your boat and not worry about anyone (easily) stealing it.
"Marine" electronics are expensive. Unless your going 20 miles offshore, I wouldn't spend the money on it.
Get automotive grade instead. This is the fuse box I used.
https://www.amazon.com/gp/product/B000VU9D20
Get a 20amp DC Breaker, and install it right at your battery. Then feed your fuse box from the breaker. That way if something happens to the line between your fuse box and the battery, its not going to make your battery catch on fire.
Next, you need to ground everything. Go to Lowes and buy a ground bar. Its a metal bar with a bunch of screws in it, Its like $5. Mount that to something that ISNT metal, you don't want to ground the boat, you want to isolate the boat.
Next, don't spend the money on that switch panel. Just buy some toggle switches.
My console
Toggle switches for marker lights, headlight, and fish finder, 2 way toggle for the bilge (on and auto with the float switch) and a momentary push button for my horn. You can get a Wolo brand car horn for $10 on amazon. Same price as two air horns, and you'll never run out of air. Its also obnoxious as heck, I've probably been ticking my neighbors off because I've been annoying my wife with it. I also installed a voltage meter, which is nice for knowing if your battery is low (around 11.5 you need to start worrying about not being able to start your engine). The LED readout voltage meter was like $3 on ebay, but I had to wait a month for it to ship from China.