Yanmar do not appear to make diesel outboards any more - I tried googling them, and got this site as one of the results -
http://www.marine-power.co.uk/d2736.htm
And no mention of diesel outboards on the new site.
I would be interested in any views or opinions on the 'long leg' outdrives mentioned in my previous post above, especially when combined with 'small' diesel engines - I suppose the main thing against them is the capital cost. And with 'average' usage the cost difference would probably not be saved during a typical lifetime of say 100 hours use each year.