The Operation manual for my 186D is about 100 pages, about 1/4 inch thick and contains specifications, layout diagrams,operation instructions, maintanance instructions. The Parts catalog is about an inch thick and contains exploded parts diagrams and parts lists on the facing page. There is an index in the back. Yanmars diagrams are first class. The Service manual is about 1 1/4 thick in a looseleaf notebook. It has 2 sections repair and operation. Each section is broken down into systems (ie.fuel/air,electrical). There are clear black and white photographs and color diagrams as well as nice drawings and pull out sectional views. Some users have reported that the manuals they have bought have been photocopies and the photographs are very hard to see. There are often Yanmar manuals up for sale on Ebay. Be careful, when I got the service manual a used one sold on Ebay for more than I payed the local dealer including sales tax. I actually have read some of the manuals. Even though the manuals might seem a little expensive I would recomend them to Yanmar owners.
Chris