Anybody know Onan generators?

[snal]

I'm putting one on my pontoon, I picked this up at a yard sale, it's an Onan 2.8, it has what appears to be a wiring harness for a dash mount start/stop switch. Wires are red/orange/yellow/brown/black, anybody know what is what? Or where/how I can find this info? Also, how should I ground this unit when I install it...just to the generator (isolated from the toon frame), or also to the frame of the toon?
TIA