Mercury Mariner Outboards 2.2 / 2.5 / 3.0 Service Shop Manual, Page 47Get this manual
Install piston ring (a) using Piston Ring Expander Tool (91-24697) as shown IMPORTANT: Piston ring must be installed so that the grooved end of the piston ring is toward top side of piston as shown
PistonInstall Piston so Arrow is Facing Down Toward Exhaust Port
Secure piston pin in piston with new "G" lockrings (a) as shown Make sure lockrings are seated in grooves