1998 Mercury 9.9/15HP 4-stroke outboards factory service manual, Page 215Get this manual
CYLINDER BLOCKCRANKCASE
Thermostat, Exhaust, and Breather Cover Installation
1Install new gasket and breather cover
a-Gasket (New) b-Breather Cover c-J-Clips (2) d-Washers (3) e-Bolts (3)M6x20 Breather Cover Bolt Torque 70 lb-in(8 Nm)