Had a new to me occurrence this morning at our marina. My wife and daughter decided to spend the night at the marina after our weekend outing. My wife called me at 6am to say that the CO monitor was going off in the guest stateroom where my daughter was sleeping. She knows the drill so she woke up my daughter and got the the boat open and put a fan in place to get the air flowing. I had her check the docks to see if someone had a something running and sure enough across the fairway there was someone’s boat running upwind from our slip. Never thought CO could be an issue at this distance but there it was.