Aobbmok DC 12V 10RPM Worm Geared Small Motor 6mm Female Shaft High Torque Turbine Reducer

For some reason, these only have screw holes on the same side as the shaft, which might be an issue for you if you want to mount a pulley as far down the shaft as possible, but otherwise, these are extremely powerful, very consistent, and pretty quiet if you mount them to something that doesn't amplify vibrations easily. In your hand, they're quieter than a desk fan, but sitting on a wooden board, it can sound like a power drill.

Well made motor that is powerful and quiet. There was some gray grease leaking out of the shaft that implies that it was well packed with grease in the factory - great!

Bought this to automate a grain mill. Does what I expected.

Works as expected. Good for holiday projects.

I use this to open and shut a chicken door. It works great.