I have the same type of setup. The photo is old, the outboard is no longer with me, but the concept is the same. Mount the outboard on the swim step, which serves a couple of things:
1) It's now a trolling motor
2) It works with the autopilot and helm if set to center of the boat (using ropes)
3) It can push the boat in calm waters 3+ knots
4) Can serve to dock the boat if the engine fails.
So, yes, it's an "emergency" backup, but fuel/range is limited.
Now... If the wind is blowing 20 knots, call for help!! But for fishing?
BTW: I absolutely applaud the OP for brilliantly thinking IN THE EVENT of an engine failure!!! The guy is thinking "extra" safety for himself and family. Yes, the inboard WILL FAIL eventually.