This arrangement is experimental yet to be tested. I'm using a standard Car alternator (Not Re-wound) with its standard pulley size. The Bukh 10DV gearbox rotates the shaft opposite to the engine when driven forward (Engine or Sail), so mounting the alternator facing backwards makes it run in its designed direction. I will modify the alternator if needed. Ideally I would like to keep it simple so that replacement parts are easier. My hull speed is 6kts but anticipate a charge at around 4 kts, anything less that 4 kts I intend to isolate the Prop-Alternator so that I don't discharge the batteries. If there is anybody out there with first hand knowledge of this set up I would be happy to 'blog' with them as there is a limited number of articles on this subject posted on the Internet.