Hubby is replacing a baystat239 t-stat with a hunter 44155c. He disconnected the old one with out labeling the wires and now can't get the new one hooked up. Help!

First of all ( I ) wouldn`t put a hunter tstat on a motorless gocart
Second ,we need to know the brand name and model number of the equipment you are trying to control
Third,It does look like the model 44155c is a heating /cooling tstat,so I hope you don`t have a heatpump
4th, he could go the other end and check what each color of tstat wire is hooked to in the furnace/airhandler
5th, tell him to be sure and kill the power to the furnace before attempting to replace the tstat (don`t want him to blow a transformer)
6th,, get him to take the hunter back and buy a Honeywell
7th ,we will be glade to helpif you can give us more info

According to hubby furnace is a goodman model number ARUF182416AA a/c unit is a trane

What color are the wires that the thermostat connects to.

Black
Green
Red
Blue
Brown
Yellow
White
Orange

Here is a chart of standard thermostat wire color convention to terminals. Since we don't know if the original person that wired up your furnace followed standard color convention your hubby will need to follow these colors down to the furnace air handler and out to the air handler and tell us what terminals they attach to. This will be a good exercise to map everything out in case you need to fix something in the future, and also servers as penance for his previous mistake.

Then we can be sure what goes to what, and provide exact advice.

The Hunter should get the job done, but I prefer Honeywell for the simple reason the volume of support online, here, from Honeywell and people familiar with it.

One everything works be sure to apply a dope-slap to the back of his head for not labellings those wires. :)