Our 36' Hatteras has the older 3 knob controls for the A/C. I am contemplating a change to SMX controls for the larger salon unit. Is the installation difficult? Would this be a good change? Our current thermostat sticks occasionally and the compressor keeps runing. We do leave the A/C on when we are away to keep the humidity down. On cooler days in Miami our compressor runs until it is a ball of ice. The pressures are fine and the unit works fine again after thawing it out. The problem seems to be that the thermostat fails to shut the unit down when the boat is cold. I am not sure about this but I don't hear the thermostat click as I rotate the knob. I tried it the next day and it clicked just fine. When the unit is a ball of ice it doesn't make cold air, but the compresor is trying to run and the cooling water pump is on and flowing water just fine. That is why I am considering the SMX controls.