Ins and Outs of Maintaining an Outboard

20 May 2010 By Roger Marshall

In the old days, outboards were relatively simple. All you had to do was change the plugs, check the coil for a good spark, change the oil and the filters and you were good to go again. But take a look under the cowl of a modern four-stroke outboard and you quickly realize that you don’t know the names of half the parts, let alone how to maintain them. But there are many things that you can do for your outboard that will prolong its life.

You should do the maintenance on an outboard engine as soon as possible, after it has been removed from the water and after has cooled down. When the engine comes out of the water, it should be thoroughly flushed with fresh water to help prevent interior saltwater corrosion. Do NOT, under any circumstances, run the engine without water – this will ruin the impeller pump in a few minutes. Wash the entire engine to get rid of salt. This is a good time to spray the entire engine with corrosion guard.

Perform a visual inspection of the entire engine. Look over the prop and skeg for signs that they may have been bent or damaged. Examine the filters for any signs of contamination and ensure that no wires are abraded. Inspect the drive belts for signs of glazing or wear and pull and check the plugs for signs of coking up, overheating or oiled plugs.

Finally, evaluate the outboard’s fuel. Modern gasoline is formulated for use in road vehicles; its anticipated lifespan is about six weeks. If you expect your engines will be out of commission for any length of time, you should use a stabilizer (eight ounces treats 128 gallons of fuel) in the gasoline to prolong its life.

If the engine is going to lie idle for more than three months, consider “winterizing” it. Pull the plugs and spray the cylinder walls with fogging oil to prevent rust from forming on them. Make sure to drain all the gas from the engine or run the engine until it is completely dry of fuel. When engine is out of fuel rotate cylinders to close off the maximum number of ports. This helps to stop moist air from getting into the cylinders.

By performing engine maintenance regularly can you expect to see a season with no breakdowns. If you skimp on maintenance you may not run into problems today, but you may be shortening the life of the engine considerably – and making your own job harder down the road.

One-Hundred-Hour Maintenance

Most manuals suggest that certain maintenance jobs be done on an engine after each 100 hours of use. For the average boater, this schedule works out to about once per season, but a large yacht or charter boat may approach 100 hours of use in only a month or two.

  1. Remove and change the plugs.
  2. Change the gearcase oil.
  3. Change the engine oil.
  4. Check the fuel and make sure you use a stabilizer regularly.
  5. Change the filters.
  6. Check the corrosion control anodes and change them if they are more than half worn away.
  7. Check the power steering and make sure the hydraulic rods are lubricated.
  8. Check all the battery components and the strength of each starting battery. If you are going to leave the engine unattended for a length of time, remove the battery and keep it charged in an area where its hydrogen emissions will do no harm.