As of 2015, YamahaOutboards.com offer diagrams for Yamaha outboards in its owners manuals. The owners manuals provides diagrams showing the basic parts, operating procedures, and maintenance routines for various models of outboards.
From the YamahaOutboards home page, hover your cursor over Owner Resources in the navigation bar, then click on Owners Manuals. Select the year and model of your outboard, then click the link for your manual. The manual may appear in the browser or download to your hard drive. Check the table of contents to locate the diagram that you wish to view, then navigate to the page number indicated.