The Yanmar Service Manual ........................
......... for 1GM10, 2GM20, 3GM30, 3HM35 and "SELOC Yanmar Inboards (1975-98) Repair Manual" are two excellent technical manuals to get you through any engine maintenance. Loads of pictures so you don't even have to know how to read. I'll bet that both these manuals together are cheaper than having a mechanic adjust your valves. And then you can do it every 500 hrs. for free.Best regards,s/v Island Hunter