Check this link for a free download of the Yanmar 3GM30 service manual
http://www.motoren.ath.cx/Download.php?filename=/yanmar/YanmarGM_HMWorkshopManual.pdf
Regards
http://www.motoren.ath.cx/Download.php?filename=/yanmar/YanmarGM_HMWorkshopManual.pdf
Regards