I thought it came on but can't remember. Pretty sure the compressor was running since basically a small heat pump and runs backwards for heat. is the sea cock open? is water coming out of the bow port?
if no water is coming out but it's running you need to crack open the pump housing slightly to get the air out. I have to do this at the beginning of each season.
I do have auto/manual switch.
I actually have the owners manual in the boat if you have the same unit.
I believe the manufacture was called "airrrrr" or something strange like that. I'm getting the boat tomorrow and can get you more info over the weekend. that is if you have the same unit.
ours is a 1998 2800 scr.
found link for basic info look on page 30