[animaashi]

I have a 1983 Irwin 34 with a Yanmar 3GM 20hp diesel. I have started noticing that at about 2000-2500 rpm''s I start to get blue smoke exhaust instead of clear. I don''t get it while operating with/without load under that rpm, or over 2600-3400.I just purchased a Yanmar shop manual and I''m more perplexed than ever. Could it be the breather tube assembly, and if so, why? Any suggestions? Thanks for the help!