Battery Switch explination

[SeaEsta-12]

Hoping someone can help me with this that might have the same set up as i do.
I just purchased a used Chris Craft Launch 28 and the boat has three batteries. (Engine 1, Engine 2, House)
It also has three battery switches. (Port, Starboard, Main)
Does anyone else have that same set up, and how are they setting their battery switches prior to using the boat?
Is the Main to BOTH and Port and Starboard on something else?
My switches have four positions each. (Off, 1, 2, Both)

Thanks in advance for the help.

 

[sam am I]

Found this, diagram 3

Might get ya going, should be close.......Could also request a wiring diagram, and/or owners manual sometimes include wiring from Chris Craft