Any chance you can explain what makes the Honda so good as compared to the competition?
I ask because I'm seriously contemplating a Yahama 2800 as a generator onboard simply because I like the extra amps it can provide, and it's only 200 bucks more than MSRP on the Honda.
Just to be sure, you're talking about the Yamaha EF2800i? Open-frame inverter model?
Generally, it's best to have more generator power than you need, because you'll often find other things to power later on. So start by figuring out how much power you need now, and consider a solution that would provide some cushion. I am not very familiar with marine A/C systems, but if they are similar to those on an RV, I know 2,800 watts is right on the edge of enough power to start and run a 13,500 BTU system.
The Yamaha does offer more power than the single EU2000i Honda, and while that's an important difference, there are others to consider; two big ones come to mind:
• Portability: Will you be loading/unloading the generator or need to move it around? With a full tank of fuel, the Yamaha is 84 lbs. and 55 lbs. for the Honda.
• Noise Level: How important is noise when using the generator? Decibel measurement are good, but try to listen to both units running at idle and full throttle for a true assessment of noise, vibration, harshness to your ears. The Yamaha is 67-67 dBa, while the Honda is 53-59 dBa.
Both the Yamaha and Honda are well-made units with 3-year warranties. But what good is it if you can't get to a servicing dealer when you need help? I went to the "Find a Dealer" links for both Yamaha and Honda and searched for a generator servicing dealership in the Jacksonville, FL area. For Yamaha, there are none; the nearest is 149 miles away on near Tampa. For Honda, there are 8 dealers with a Jacksonville address. I will bet you get similar results for dealer searches in your region too.
Look at what others are using and learn from their experiences. I'll bet most are using Honda generators, and those that need more power than a single EU2000i model can provide usually get a second one (the Companion model), for a full 4,000 watts of combined power. While it's more $$ than a single 2800 watt Yamaha, you do get significantly more power, less weight, less noise. To be fair, that's two generators to change oil, drain fuel, and service.
Hope this helps...
Caveat: I work for Honda, but the preceding is my opinion alone.