Yamaha Outboard Motors Factory Service Manual F6 and F8, Page 276Get this manual
CAMSHAFT AND VALVES CHECKING THE CYLINDER HEAD
Measure: Cylinder head warpage Out of specification Resurface or replaceWarpage limit: 0.1 mm (0.004 in) Resurfacing steps: (1)Place 400600 grit wet sandpaper on the surface plate(2)Resurface the cylinder head using figure-eight sanding pattern
To ensure an even surface, rotate the cylinder head several times
REPLACING THE VALVE GUIDE