2001 Mercury Mariner 50-60HP Factory Service Manual, Page 281Get this manual
CYLINDER BLOCKCRANKCASE
Powerhead Installation
CAUTION
When lubricating the driveshaft splines do not allow any grease on top of the driveshaftGrease on top of the driveshaft will force the shaft down when installing the gearcase, causing the pinion gear to bind with the forward gearThis can result in damage or failure of the gears1Install powerhead and new base gasketTighten mounting bolts to specified torqueIMPORTANT: If the crank shaft splines do not line up with the driveshaft splines, shift the gearcase into forward, place prop on the propshaft and rotate it counterclockwiseThis will allow the splines to line up