I know this is an old thread but I will tell you what I added to our new to us boat this last summer. Let me start by say hi and been its great reading, couldn't post for awhile Thanks Katie for clearing that up. We are the 3rd owners of our 1988 Liberty Bell she is 52 x 15 single level. Got her the 1st of July, moved up from a 1972 Stardust that I had more money than brains in. See was made in Wi for a rental boat and made like a tank and with simple strait forward systems. But being built for a rental they didn't put air in her nor did the last owner. Also the wiring was not up to handling air. Only 2 breakers 15 and 20 amp with 12g wire from the shore power to the breakers. So we redid some of the wiring, added a main panel with a selector switch and breakers. We also added 2 roof top air units. After much reading and research and talking with the engineers at Coleman I went with their 13500btu Mach3 POWER SAVER model and here is way. It will run and start off a gen as small as the Honda 2000 and you can run 2 of them off a 30 amp shore power they only draw 10.2 amps each running. We ran our 2 in the last bit of the heatwave last summer with our gas elc frig on, two small battery Chargers on tv, lights at night with no problems. Just to see if I could pop the breaker, I ran our small microwave too, didn't pop. I look at putting marine air in but it was just not possible with the duct work and the amount of btu's that was recommended was eye popping to say the least.