Generator Problem

[Chris]

Recently purchased an 83 FC 35SB with the 12.5 diesel generator. With
the generator running, only one leg will work. If I turn the breaker
off inside the generator compartment, the other leg will come on and
the one that was working will turn off. I have not been able to make
both sides run. On 50amp shore both work fine. I have also noticed
that with the bottom leg on, the one that controls the mid and rear
A/C, it always reads less voltage on the AC monitor....any ideas on
whats going on? Are there any other breakers on the actual generator
that I am missing?
Thanks
Chris Reed
83 FC 35SB
Plant City, FL