DIY: Outboard Engine Spring Tune-Up

by David Eiranova
Water being pumped through the engine is used to keep the outboard from overheating.

Water being pumped through the engine is used to keep the outboard from overheating.

A spring tune-up of your outboard can go a long way toward ensuring a trouble-free summer boating season, and it is an essential part of spring commissioning for your boat. It is an easy procedure that involves both inspection and maintenance, which you can do yourself.


At the heart of the spring outboard tune-up is spark plug replacement. When you disconnect the ignition wires, be sure to remember the cylinders to which they correspond. This is easy enough with a one-cylinder or two-cylinder motor, but for larger motors it is important, because the timing is set to fire the cylinders in a predetermined order. Use a spark plug socket that has a rubber guide on the inside--this will prevent the tip of the plug from scraping the sensitive sides of the cylinder. When applying torque to the new plugs, do not over-torque or you might damage the plug.

Gear Case

Check the condition of the lower gear-case oil. Near the bottom and on the side of the lower unit is the drain/fill screw. Unscrew it and allow a small amount of gear oil to fall into a container such as a metal pie plate. If the oil appears milky or cloudy, it’s likely that you have a leak, probably in one or more of the lower unit seals. This is a serious matter that should be corrected promptly, because water in the gear case can lead to expensive repairs.


Visually inspect the gas tanks for corrosion and check to see if the priming bulb is firm and resilient (a bulb with cracks or one that collapses should be replaced). Top off the battery cells with distilled water and charge the battery or batteries. If the terminals show corrosion, clean them with a gentle solution of baking soda and water. Check the fluid level in the hydraulic tilt and trim system if your motor is equipped with one. Any leaks should be addressed before launching the boat. Since you have your tools out, you might as well pull off the propeller to check for any damage or fishing line. Keep track of the order in which the various washers, nuts, sleeves and adapters came off--this will make it easier to reinstall the prop. Take a look at your sacrificial anode (also known as a “zinc”). If it appears to be heavily corroded, replace it. An anode in good condition keeps the parts of your engine that sit in the water from corroding. Another good practice to follow is to inspect the steering, shift and throttle cable. Cracks or bulges in the cable outer jacket could indicate corrosion in the cable.

About the Author

A reporter since 2005, David Eiranova wrote for "The Lunenburg Ledger," from 2007 to 2009 and has served as a correspondent for "The Lowell Sun." He holds a Bachelor of Arts in economics. Since 2007 he has been the director of publicity for the Acton Community Chorus.

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