Strange Electric issue with new stereo?

I install a new Kicker gauge style radio in my 185 sport (2006). I ran a positive to terminal #7 on the fuse box markered radio with a 10 amp fuse. I used the ground terminal on the fuse box upper left-hand corner. No other positive wires were used or hooked up.

Whenever I turn on anything electric on the boat the radio will come on automatically. The radio will come on with the key off by itself as well???? I am the son of an electrician and can not figure out how I could be back-feeding the stereo.

Thoughts??? Tim....thank you

A few things to try. Take the ground off and see if it still occurs. Of course it should not unless it is getting a ground from some where else. Sounds dumb, but need to start somewhere. If not, move the grould to a different location. If occurs, move power to different HOT location and see if that helps.
There seems to be voltage getting through to the stereo and activating the auto on. Other thing would be to put it on a separate switch so you can isolate it shutting down the power feed to it.

So the radio has a constant supply of +V? Does the radio have some kind of auto-on feature? I would check the installation manual for the stereo.

The KMC2 is a 2-wire power harness. You can wire the red to a constant, which it sounds like your #7 fuse is, and use the KMC2's power button to turn it on/off. Or, wire the red to a switched source, like the key (which I hate) or a rocker/toggle.