Is 7.30 a good time when rowing for 2000meters on a rowing machine.?

This would depend on your sex, age, fitness level, and goal. If your goal is general physical fitness, then yes this is a good time (especially good for a woman). If you want to be on a crew team, then this would be a good starting point for a junior guy, and would be a very good time for a junior girl. At the collegiate level however this would not be a good time for an experienced guy. Also, note that size plays a factor and the larger you are the better time you will need.