I run a presonus 24.4.2 Studio live mixer/interface and on every project I start need to go in an assign it to send the output of the master bus in sonar to the proper input on my board.  I am sure there is a way to set this default and I can't seem to find it.

Make your own templates. 
Easy is to open the Normal template , modify to suit your needs, and save it. You can actually save it as a CWP file too. That's what I do now. I just name them and keep them in a folder named "templates" 
I have a template for each type of session I might need. 
 

Right click the bus and choose 'Set as Default Bus'

I will try that Gswitz, Thanks