TPD, read through the post I made in this thread:
viewtopic.php?f=2&t=21825&p=133807&hilit=generator#p133807 I can't take credit for the bulk of the information in it, but I can tell you that the person who wrote the info (that I simply copied and pasted) is EXTREMELY knowledgeable about anything boat related - puts me to shame!
One thing I'll add... keep in mind where you are putting the genny has a decent chance of blowing the CO back into the cabin. An installed genny will typically have the exhaust exiting the side of the boat. As such, the wind will blow the exhaust away (since an anchored boat always points into the wind). Having a portable one back at the transom could invite the "station wagon" effect to happen and pull the CO right back into the cabin.
Also, you're going to want to mount the A/C unit in a dry area with a good supply of fresh air. A damp area is bad for the machine (corrosion) and for you.
I'm not directing this statement specifically at you, but just offering it as something to think about in regards to portable genny's and the "it worked great" mindset... How about this statement: "I drove without my seatbelt the other day and I was totally fine. Since nothing happened that time, I will continue to not wear my seatbelt since I'm sure nothing will happen in the future".