HOW TO Troubleshoot your outboard engine

Small four-stroke outboard engines are pretty simple. Max Mchugh of Marine Matters explains how to tackle the most common problems...

1 FUEL

The main reason for your engine not working will be the fuel system, often because fuel has been left in the engine over winter. The fuel goes through a chemical reaction producing ethanol, which will prevent the engine from running. There may also be dirt blocking the filter, lines or carburettor. To clean, remove the flywheel cover and engine cowling, and then undo the fuel tank. Take the tank out and remove the fuel line, draining the tank into a bucket. Flush the tank through with clean fuel. Check the filter is clear and rinse with clean fuel if needed before reconnecting the tank.

2 CARBURETTOR

Next check the carburettor. Turn off the fuel tap, then open the drain screw on the side of the carburettor and drain into a bucket. Close the drain screw, open the fuel tap and add clean fuel. If the engine still doesn’t run, you may need to clean the carb out, either with a can of carb cleaner, or at a workshop that has ultrasonic cleaning.

3 SPARK PLUG

Next check the spark plug has a spark. You can use a spark plug tester, connected between the plug and the ignition (high tension) lead. If you don’t have a tester, remove the plug, connect it to the lead, then touch it on the engine body before pulling the cord. You should be able to spot the spark. If you can’t you may need a new plug.

4 KILL CORD

If the kill cord is fitted correctly, it’s worth checking the stop button. It has a spring inside, but this can degrade over time, especially if the kill cord has been left attached. You may need to replace the button assembly if it doesn’t pull back in.

5 COOLING SYSTEM

If your engine has sea water cooling (some are air cooled) and you haven’t flushed the engine for a while, you can get salt build-up in the engine. Run the engine in a barrel of fresh water, or use a hose and a set of flushing earmuffs. Check the water tell-tale has a good flow before you set off.

Small engines don’t have an overheat alarm but will shut off as a failsafe. If you need to check the thermostat, take it out and place it in boiling hot water, and you should be able to see the spring move. If it doesn’t, you’ll need a new one.

6 OIL

Four-stroke engines have an oil sump for lubrication. It should say how much oil you need. Fill it slowly and check against the sight glass. If you do overfill it, drain into a bucket.

7 END OF SEASON CARE

Make sure you drain the fuel out of the carburettor or run it dry. It’s also worth draining the fuel tank and giving it a clean. Leave the spark plug in to keep moisture out. If you are storing it on its side, ensure it’s on the correct side.