10 volts is borderline, but as long as it holds it ought to be okay. have you tried jump starting it with your car? or another known good battery of similar size?
i would get a set of jumper cables, From the buggies battery take the positive straight to the + lug on the starter, and ground from the battery to a bolt on the frame or other good ground. then try to start it, if it spins over good with the jumpers, there is an issue with the wiring, not being able to carry the amperage. If not either battery or the starter, or excessive compression load on the engine.
next i would use a car battery, or better yet a battery of good condition and similar in amps, go from the + on that battery, to the + on the starter, and - to a good ground on the buggy,
try to start it.
Does it start fine like it's supposed to? If YES, Battery issue. if NO, probably a starter issue or excessive compression load on the engine and starter.