1998 Mercury 9.9/15HP 4-stroke outboards factory service manual, Page 284Get this manual
NON BIGFOOT 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 plugs2Apply 14 in(6.4 mm) diameter bead of RTV Sealer on water pump base
RTV Silicone Sealer (92-91601-1)