I am working on one such project. I have characterized the motor I have as a generator. The generator constant for open-circuit voltage is 26.5 rpm per volt, and output resistance is 1.24 ohms. I should be able to do with a direct-drive propeller. Airgap clearance is small, and rigidity is low, so it will probably suffer from rubbing of magnets on stator due to gyroforces in a windmill situation.
Performance quoted is presumably for the machine when cold.
Resistance of windings incerases significantly with temperature, which can lead to much higher losses during sustained runs. I sell plans for building a much simpler machine with similar output. Using scrap materials, you keep the cost to a minimum. I live in Scotland in the UK, British Isles. If you live in the USA, the best way to pay is to send me dollar bills in the post.