2007-2009 Yamaha F15/F20 Outboard Service Manual, Page 288Get this manual
TECHNICAL FEATURES AND DESCRIPTIONS 1POWER HEAD
1) PISTON, CON-RODCRANKSHAFT
The crankshaft is designed with off-set from the center of cylinder to make space for the electrical components installationThe correspondence marks on con-rod and its cap show UP sideThe piston and con-rod have to be installed with proper direction because of the off-set pistonTwo kind of oversize piston is availableSTD 1st OS 2nd OS Piston diameter (mm) 62.950 62.965 63.200 63.215 63.450 63.465 (63.00) (63.25) (63.50)