Mercury Mariner 30/40 4-Stroke Outboard Service Manual 1998, Page 418Get this manual
NONBIGFOOT GEAR HOUSING
Gear Housing Installation
1Position shift lever in NEUTRAL gear position2Tilt engine to full "Up" positionEngage tilt lock lever3Shift gear housing into NEUTRALPropeller shaft will rotate freely in either direction
IMPORTANT: Liberally apply 2-4-C Marine Lubricant wrreflon to drive shaft splines4Position drive shaft into drive shaft housingMove gear housing upwards in drive shaft housing while aligning both shift shafts, water tube seal and drive shaft splinesNOTE: If the drive shaft splines will not align with the crankshaft splines, rotate flywheel slightly while pushing gear housing into drive shaft housing