1998 Mercury 9.9/15HP 4-stroke outboards factory service manual, Page 270Get this manual
NON BIGFOOT GEAR HOUSING
3Install upper drive shaft bushing assembly using Drive Shaft Bushing Tool (91-824790A1)
NOTE: The upper drive shaft bushing is pressed into sleeveIf the bushing is not worn into the sleeve or the bushing is not spinning within the sleeve, the bushing alone may be replacedPress the new bushing into the sleeve using suitable mandrelIf the sleeve is damaged, the bushingsleeve assembly must be replaced