Yamaha Marine Outboards F4A/F4 Factory Service Manual, Page 196Get this manual
CRANKCASE, CRANKSHAFT AND CAMSHAFT
Piston ring installation 1Install: 9Oil ring 92nd piston ring 9Top piston ring NOTE: 9Install the oil ring, by first fitting the expander ring and then installing the side rail ring9Make sure that the "2N" mark is on the 2nd upper ring to install the piston9When reusing the top ring, be sure to mark and install in the original upward position9After installing the piston rings, check that they move smoothly