Mercury Mariner 8/9.9HP 4-Stroke Factory Service Manual, Page 164Get this manual
Powerhead Installation 1Remove all old gasket material from power head base and matching drive shaft housing surface2Install powerhead gasket, dowel pin, O-ring, damper and seal
4Install trim covers and screws
a Gasket Dowel Pin O-Ring Damper Seal
aScrewTrim Cover