When the motor in my loud rangehood died I just pulled it out and installed an inline centrifugal fan in my roofspace. Not as quiet as a fully externally mounted motor but much quieter than having one at face height inside your hood.
I used this fan here which you can get with a wireless touch panel for controlling it.
http://www.mingfans.co.nz/index.php/product/index/id/50.html