The Engine

• Most maintenance is performed before winter lay-up. If you live in a climate that allows year-round boating, perform maintenance annually. Change the engine oil and filter. Change the fuel filter/water separator. Tune the engine by replacing the sparkplugs and ignition parts, if so equipped. Flush the raw water from the cooling system and replace with marine anti-freeze. Check all belts, hoses and clamps. Replace them if they show signs of wear. Clean the flame arrestor and replace the PCV valve. Clean up any oil spills or grease from the engine surface and the bilge.
  
  

The Stern Drive

• Change the stern drive gear lube annually. Carefully inspect the old lubricant for moisture or metal filings. These are signs of trouble that need to be corrected. Remove the propeller and grease the shaft. If the prop is damaged, take it to a marine service provider for repair. Prop repair is not a do-it-yourself project. Every three years, the drive should be removed for proper inspection of the U-joints and bearings. Check the engine alignment with the proper tool, and replace the impeller inside the raw water pump.
  
  

Precautions

• A service manual is a wise investment when performing maintenance on the Mercruiser. Make sure that the manual you purchase is for your particular model and year. If a procedure calls for the use of a particular tool, use that tool. Do not improvise. In addition, if you feel that a task is beyond your expertise, take your boat to a qualified Mercruiser mechanic.