Mercury Mariner 25HP 4-Stroke Outboard Service Manual 1997, Page 255Get this manual
General Service Recommendations There may be more than one way to "disassemble" or "reassemble" particular part(s)thereforeit is recommended that the entire procedure be read prior to repairIMPORTANT: Read the following before attempt-
Inspect all bearings for roughnesscatches and bear ing race side wearWork inner bearing race in-andoutwhile holding outer race, to check for side wearWhen inspecting tapered bearingsdetermine condition of rollers and inner bearing race by inspecting bearing cup for pittingscoringgrooves, uneven wear, imbedded particles andlor discoloration from over-heating Always replace tapered bearing and race as setInspect gear housing for bearing races that have spun in their respective boresIf race(s) have spungear housing must be replaced Roller bearing condition is determined by inspecting the su rface of the shaft that the roller bearing supportsCheck shaft su rface for pitting scoringgrooving, imbedded particles, uneven wear andlor discoloration from overheatingThe shaft and bearing must be replaced if such condition exists