1995 Mariner Mercury Outboards Service Manual 50HP 4-Stroke, Page 127Get this manual
Valve Guides NOTE: Inspect the valve guides for wear or damageIf valve guide wear is out of specification, replace the valve guideMeasure valve guide boreInstall the new valve guide and circlip using valve guide installer bushing along with the valve guide remover
aValve Guide Remover (91-809495A1)Valve Guide Installer Bushing (91-809496A 1) 53736
After installing the valve guide, ream the valve guide using valve guide reamer to obtain proper stem-to-guide clearance