the important thing to remember about DC motors when trying to run them as a generator, is what the working rpms of the particular motor are. eg my 12v dc air horn compressor is rated at about 2000rpm, totally useless for a wind turbine because theres no way Im gonna spin a 6ft blade at 2000rpm. Ideally you would use a low rpm motor <500rpm without a gearbox, it must be direct drive, the gearbox will add too much drag to make it a viable proposition for DIY use. So to answer your question, yes it will produce as a generator but at what revs, 1500rpm's? then the question becomes, what method are you going to use to spin it at its working revs?