How to repair your outboard engine


How can a day on the water go awry? 
Let us count the ways. Better yet, let us count the ways to diagnose (and cure) problems, or at least make it back to the dock under your own power.

1. Loose throttle cables

Few things are more disappointing than turning the ignition key and being greeted with stony silence. First, check to see that your throttle is in the neutral position, as most engines won’t start in gear. Seems straightforward, but loose throttle cables can complicate the issue. In this case, you may have to jockey the throttle lever back and forth several times, while keeping the ignition key turned, before you find the right spot. Don’t forget to take ’er to the marina 
to have those loose cables tightened.

2. Kill-switch killjoy

The engine won’t start if you forget to insert the kill-switch clip. If your boat or engine has a kill switch, check that the clip is firmly in place, or try removing it and reinstalling it. If the engine still won’t start, you may have a loose connection between the kill switch and ignition. Check that all wires are firmly connected and free of corrosion. If corroded, try some WD-40 or a similar spray oil. Smart boaters keep a spare kill-switch clip onboard in case they lose, forget, or break the first one.

3. Terminal conditions

If the engine still doesn’t produce any 
activity or sound, check the battery terminal connections. Terminal post nuts often loosen over time because of vibration; if they’re loose, tighten with a wrench. By the way, if you have wing nuts on your terminal posts, replace them with nylon-insert locknuts, which will not back off. If the terminal 
posts or cable terminals show signs of corrosion, spray some WD-40 on them or scrub 
them with baking soda and a wire brush. Replace all corroded cables and leads as soon as possible.

4. Deadbeat battery

If the battery connections appear fine, check the voltage on your cranking battery using a voltmeter. The battery should register at least 12.4 volts. Anything less and you’ll need a jump-start (see “Band-Aid Fix: Jump-starting 3 Ways,” at right). Or you can try to start the engine manually by spinning the flywheel with a pull cord (often provided with outboard engines up to 40 hp; if it’s not installed, check your manual to see how).

5. Damaged leads

If the engine is turning over and getting 
fuel (the tank is connected and the primer bulb is hard, right?), examine the spark 
plug leads and boots. The boots should be firmly seated at both ends and free of corrosion. If you see signs of damage, such 
as cracks or areas of exposed wire (mice often chew on the insulation during winter storage), replace the leads or boots as 
soon as possible.

6. Fouled plugs

If the leads and connections are fine, check for fouled spark plugs, especially if it’s been 
a while since you changed them or the engine is running rich, causing carbon deposits to form on the electrodes. Change the plugs if the electrodes are fouled or the plugs show signs of damage, such as thick, black carbon buildup or residue on the plug electrodes, 
or cracks in the ceramic housing. Keep a set of spare plugs (gapped, if necessary, to the manufacturer’s specifications) onboard in a waterproof bag—or better, a vacuum-sealed bag, because humid air contains moisture—along with a socket wrench set, preferably one with a rubber gasket to hold a plug in place as you remove or install it, and with an extension, if necessary. Another tip: Use a 
6″ section of 3/8″-dia. fuel hose to grip the end of a spark plug for easy removal and installation. If changing the plugs and checking the leads doesn’t help, call the pros.

7. Stuck starter

If the engine won’t turn over, and you hear a “click” from the powerhead, you may have a starter issue. Remove the cover and see if the starter pinion gear is popping up to engage the flywheel when you turn the key. If not, try  starting the engine manually by spinning the flywheel with a pull cord (see “Deadbeat Battery,” p. 108), or try the hammer trick: It’s a bit crude, but a light tap or two on the starter housing with a rubber mallet could “unstick” the starter motor and get you back to the dock in a pinch. It can damage the magnets inside, though, so don’t use too much force. Also, don’t forget to take the engine in—your starter or solenoid may need to be replaced.

8. Breathing problems

Here’s another common and easy-to-fix problem, especially with engines that have portable fuel tanks. When transporting the tank, many boaters close the tank vent to prevent vapour and fuel from escaping. However, if you forget to loosen the vent screw, a vacuum will eventually form as the engine runs, cutting off the fuel supply and shutting down the engine. A sure sign of fuel starvation is a collapsed primer bulb. The solution is to loosen the vent screw and pump the primer bulb until it is hard.

9. Alarming heat

When an alarm sounds, shut down immediately. Consult the owner’s manual first. One of the main reasons for a blaring alarm is a high engine temperature (other culprits: low engine oil or low oil pressure). Look for debris, such as a plastic bag or vegetation, block-ing the engine’s cooling-water intake. If it’s 
clear, turn on the engine briefly to make sure 
cooling water, the telltale, is streaming 
out. If not, try poking the intake with a short length of heavy monofilament fishing line to clear any blockage hidden inside. Failing that, you may have a faulty thermostat, sensor, or water pump, which warrant a tow to shore.

10. Oil crisis

Or the alarm may signal low oil level. Refill the oil if it’s down, but if the alarm continues after you’re going, check for a thirsty reservoir: Newer-model two-strokes (chiefly those over 90 hp) have an oil tank separate from the engine, but some also have an internal reservoir. This reservoir, often mounted in front of the powerhead, holds enough to prevent oil starvation should the main tank run dry. If the oil in the reservoir drops below the sensor level (usually 1/4 full), the alarm will buzz until you’ve refilled. Loosening the top vent screw while the engine runs will sometimes refill the tank, or do it by hand, using a small funnel.