I also have a 38CC Irwin
My boat has a Autohelm 6000 and the Navigation
Interface which used the signal from Loran
C to guide the boat.
I am told that it will accept NEMA 0183 instructions, and translate to the course computer, although I haven't managed to do so yet. I did get it to link up once, but didn't realize till later that I had the breaker to the drive unit off by accident
I'm courious to see what we can find out, as I think I will have to upgrade mine before long.