If it's adjustable it will have a screw that you turn for more or less. I agree with 7.0 -7.7 volts. If it's not adjustable find out how much you are getting out of it. If you need one I have a couple laying around for shipping cost.
1953 Chevrolet 3600 Fried Green T'mater (Vern) In the Stovebolt Gallery Caution: Political Statement Man who runs in front of car gets tired, man who runs behind car gets exhausted.