Ron, now is the time to find out if the 7-wire cable is safe to use for the purpose. My concern is the insulation rating for the wires in the cable, If the cable is designed for thermostat use, for example, you want it replaced immediately. What you need is a cable (or individual wires) with insulation rated at 600V or better on each and every wire in the group.
No, it's not thermostat wire. The insulation is fairly thick. I asked him about it and he said it was rated at 600 volts, but the colors do not match the generator & transfer switch colors.