Ted,
True 'white smoke' suggests that 'water vapor' maybe entering the system some where.
However, before jumping to that conclusion, especially if you've recently changed the
fuel filter, check to see that you have bleed all the air out of the injector
fuel line.
Finally, for a better chance at help try going to Yanmarhelp.com website. They've set a forum up for each Yanmar diesel model, which may help you identify the source of the problem.
Regards,
James