Would it be theoretically possible to connect a water wheel turbine direct to a reworked gas generator. Disconnected from the gas motor. Leaving the generator section. To power the generator? I am going to build the turbine for use at the area for wife's small nursery. Thank you

Yes it is possible to do it. Your main worry will be the steady source of water. Here is an example of one.

12 inch Pelton Water Wheel Turbine