Yanmar had a 27 and a 36 that sometimes could be found in the Caribbean, but neither of them passed emissions here and weren't sold in the US. The few actual reviews from users while we were living in Germany reported reliability but a bit more weight and vibration were compromises. Pricing was high compared to equal HP gassers. There was another thread a couple of weeks ago that spoke about higher HP Oxe diesel outboards being spec'd by the military. It could bring something to the public, but higher HP and the weight to go with it. Here's the link:
http://www.trawlerforum.com/forums/s6/oxe-diesel-outboards-29555.html
Here's some spec's on the Yanmar 27 sold on E-bay a couple of years ago.
Specifications
Model = Yanmar D27 Diesel Outboard
Type = Vertical crankshaft, 4 cycle
Cooling = water cooled diesel engine
Maximum output/RPM = 27hp (19.9KW) at 4,500 rpm
Dry weight = 181 pounds
Fuel = Diesel, kerosene + oil, or biodiesel
Bore and stroke = 3 - 70x70mm (808cc)
Combustion system = Direct injection (by unit)
Number of cylinders = 3
Valve Driving = Timing-belt driven/OHC system
Cooling = Direct seawater cooling
Starting = Electric or emergency recoil rope
Steering system = Tiller (bar handle)
Speed control system = Tiller (bar handle)
Tilt up system = Manual with spring assist
Gear reduction ration = 1.846 (both forward and reverse)
Clutch = Dog type, by clutch lever operation
Propeller = 3-blade, spline coupling
Engine lubrication = Forced lubrication pump
Lower unit lubrication = oil bath