1986+ Mercury 6/8/9.9/10/15HP 2-stroke Factory Service Manual, Page 253Get this manual
GEAR HOUSING
Installation
WARNING
To prevent accidental engine starting, remove and isolate spark plug leads from spark plugsBEFORE installing gear housing1Remove and isolate spark plugs leads from spark plugs2Place shift linkage on engine in FORWARD gear position3Tilt engine to full up position4Place gear housing in NEUTRALPropeller will rotate freely in either direction when gear housing is in NEUTRAL5Position shift shaft as shown when measuring distance in Step 66Distance between top of water pump base and center of hole, must be as specified belowTurn shift shaft clockwise to decrease distance or counter clockwise to increase distance