Mercury Mariner 8/9.9HP 4-Stroke Factory Service Manual, Page 208Get this manual
5Install gear housing as follows: aApply light coat of 2-4-C wTeflon Marine Lubricant onto the drive shaft splinesbInsert the drive shaft into the opening in the upper part of the mid sectioncInsert the shift shaft through the rubber seal in the mid sectiondInsert the water tube into the water tube guide 6Install bolts and torque to 15.0 lbft(20.3 Nm)a
NOTE: It may be helpful to slide the water tube guide onto the water tube and then reconnect the water tube guide onto the water pumpeRotate propeller counterclockwise while pushing upward on gear housing to align drive shaft splines with crankshaft splinesfPlace the gear housing into neutral by pushing down the shift shaft into the neutral detent position (propeller will rotate freely in either direction)aBolts [Torque to 15.0 lbft(20.3 Nm)]