12v breakers rather than fuses at the helm? That's handy. How many breakers? That might be it. There aren't that many 12v circuits on a 2600.
I found this schematic, which is probably the best I've ever seen:
https://s2b4aa72b8b1c7323.jimcontent...compressed.pdf
It looks like it includes color coding. However, it doesn't show where the 12VDC panel is actually located. As stated, it is typically under the helm.
I'd turn everything 12VDC on, then start shutting of one DC breaker at a time and see what shuts off.