1998 Mercury 9.9/15HP 4-stroke outboards factory service manual, Page 288Get this manual
NON BIGFOOT GEAR HOUSING
21Check shift operation as follows: Place shift lever in FORWARDGear housing should ratchet when propeller shaft is turned clockwise and resistance should be felt when propeller is turned counterclockwisePlace shift lever in NEUTRALResistance should NOT be felt when propeller shaft is rotated in either directionPlace shift lever in REVERSEResistance should be felt when propeller shaft is rotated in either directionIf shift operation is not as described, recheck the coupler installation procedure