Mercury Mariner 25HP 4-Stroke Outboard Service Manual 1997, Page 16Get this manual
Inspection And Maintenance Schedule To keep your outboard in the best operating condition, it is important that you outboard receive the periodic inspections and maintenance listed in the Inspection and Mai ntenance ScheduleWe urge you to keep it mai ntained properly to ensure the safety of you and you passengers and retai its dependabil-
Every 100 Hours of Use or Once yearly, Whichever occurs first
1Lubricate all lubrication pointsLubricate ore frequently when used in salt water2Change engine oil and replace the oil filterThe oil should be changed more often when the en gine is operated under adverse conditions such as extended trolling
3Inspect thermostat visually for corrosion, broken
spring, and to determine that the valve is completely closed at room temperatureIf questionable, inspect thermostat as outlined in Section 48Thermostat" 4Inspect and clean spark plugs5Check engine fuel filter for contaminants6Adjust carburetor(s) (if required)