AC
We installed a 12 BTU on our O'Day 28 and this was the correct size for us. We are in Texas and the heat can be over a 100. I think the 16000 BTU unit should be correct for the 34. We did not install the reverse cycle due to space limits; however, several boats near us did and found the heating system did not work as the water temperature dropped below 40 degree. One thing make sure the water pump is adequate size for your unit. The one sent with our system was to small and we had to increase it due to the temp of our water.Good Luck