you can. you may have to change the pulley over, and it probably wouldn't last very long if you put full load into it (used all of your electrics like headlights, heater motor, radiator fans) as you would be trying to get more current from it than it can produce. you can't damage anything except the alternator itself though, unless your fuel pump also gets a low voltage due to too much current draw and then you could melt the engine as the pump won't be able to supply enough fuel.

best get a proper one eh?