While cruising last summer, I met a fellow who told me he was running his Yanmar 30GMF on a mixture of standard diesel and biodiesel fuel. He claimed quicker starting, smoother running, far less soot on his white topsides, and less odor. He also reported that he'd gotten the blessing of Yanmar USA to try this fuel mix--and that he'd never go back to straight diesel.
Biodiesel is relatively expensive and not widely available, but that wasn't an issue for this particular owner, who--like many of us--powers little and fills his tank only once a year.
I'm wondering if others have tried biodiesel, and what they can report about the results.