Ok. The ones you did are what seemed to work for me.
If you like here is a few more steps... Sorry I didn't mention them before.
1. Try someone else's iPhone (same model if possible, same IOS) and with the new cable. If it charges and your's doesn't, the problem is somewhat narrowed down to your phone.
If that doesn't work, try an android phone just to see if the USB power is actually working with another device other than Apple.
2. If that doesn't work, and there is no USB power coming from the head unit. Unplug the cable that runs from the USB connector to the back of the stereo. Then reconnect. Could be that this cable has gone bad. In that case, try plugging in your USB cable to the one that directly comes from the back of the head unit. Just to test that segment, if it is in fact a two segment wire.
3. If that doesn't work, ...hate to say this but I'd unplug the other inputs aux, am/fm/Sirius etc at the back and just leave the USB connection and narrow down. And unplug the remotes that connect to the deck at the same time. So all that remains are the speakers, power / ground / amps and of course that USB connection causing the problem that are physically connected. It's fairly accessible on my boat, not sure about yours.
4. I may still be under warranty, at this stage if you make it this far... It might be the head unit, I'm reluctant to recommend changing that because these cables get fussy and replacing the head may be a waste of 200-250.00.
Below is the wiring diagram.