Hi Tony,
Yes, I bought a 914i a couple of years ago while at the London Boat Show thinking it would be the answer to ensuring my batteries were always fully charged, but it was very unreliable such that I took it off. Initially it seemed to work well, but some seven or eight months after installation one of the brushes became worn, turned somehow sideways and jammed within the turret such that new brushes and turret housing were required. Then over the winter it couldn't handle the wind speed and again the brushes and turret were damaged, the rotor windings burnt out and the charge regulator overheated, though this latter problem was not identified until later. Marlec were very good in that everything was repaired under warranty, except for my confidence in the machine. Later when the charge regulator problem referred to earlier was identified, that too was repaired under warranty, but with the system now working I decided to get rid, and go down a different route and installed a 100w solar PV panel (eBay £140 flexible panel). The wind generator and it's support were taken down and sold off, but the charge regulator was retained.
On a B36(2002) there is not much space for a solar panel to be fitted, but next winter I'm going to have a simple arch made to fit at the stern where I will place the current solar panel and another. At present 100w of solar panel just about looks after my batteries, but with not much to spare, and hence the intention of getting the second panel. With hind sight I wish I'd not bothered with the 914i.
As for the solar panel, it works brilliantly, no stress at all on whether the wind is going to be too strong, it's a bit like the Ronseal advert in that it just gets on does what it is designed to do, and without any fuss.