You definitely bring up a good point about the genny/no genny vs CO detector thing. I can only answer from having experience with multiple, "cabin/cruiser" style boats. While those were all stern drives or inboards (gassers), and of course had CO detectors, the detectors were ALWAYS hard wired. I've seen this in many other cabin/cruiser style (including go-fast boats) as well, although I didn't personally own them.
I think the idea is that... as an example... you're in your boat sleeping while in the slip with everything turned off. Your dock neighbor has his genny running and the exhaust floats into your boat and into your cabin. You don't wake up.
If a boat happens to have a butane or alcohol stove, that's another reason to have a CO monitor. Possibly using a portable heater is another reason to have a CO monitor - which would obviously not be an issue with a bow rider.
As another example... I've personally had the CO detector's alarm sound after working in the cabin for an extended period of time (happened twice). The door was open, but the boat was shrink wrapped. Now, I don't fully understand this since I don't exhale CO, I exhale CO2. But, none the less, it did happen. Just can't explain why.
So, while I don't know whether it's "required" by USCG for an outboard with no genny, I do think it's a good idea. And, from my experience, anytime there has been a CO monitor installed by the factory (regardless of boat brand), it has ALWAYS been hard-wired -- which was my main point to you -- look for a hard-wired connection (of course, maybe Grady does it differently than every other manufacturer I've seen so far!). The other stuff is really just a "side note" for discussion.
