Troubleshooting an Outboard That Won't Start

An outboard that fails to start is frustrating enough when you're at the dock, but can be downright alarming when you're out on the water. The most important thing to do if your outboard won’t start is to keep calm. 

Outboard won't start troubleshooting

Losing your temper or panicking won’t fix anything. Although many issues can cause a no-start, several of the most common problems are easy fixes. Stay calm, take a deep breath, and try these troubleshooting tips for when your outboard won’t start.

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Outboard Troubleshooting Tip 1: Check the Obvious

The simplest things that would prevent an engine from starting can be easily overlooked, but start with the obvious first. Most outboards won't start unless the shifter is in neutral. 

Outboard troubleshooting kill switch

Double-check that the motor hasn't been left in gear by moving the shifter in and out of gear a couple of times. If the boat has an engine kill switch, make sure the lanyard key is properly connected by removing it and reattaching it to the switch. If these simple remedies don't solve the problem, the next step is to look at the battery.

Outboard Troubleshooting Tip 2: Check the Battery

Forgetting to turn on the boat's electrical circuit via the battery switch is another common error that takes a second to fix. If that doesn't solve the problem, check that the battery switch is on, and that the battery cables are free of corrosion and securely attached to the battery. 

Outboard troubleshooting battery switch

If the terminals are corroded: 

  • Disconnect the cables
  • Clean the terminals with a wire brush
  • Reconnect the cables
  • Cover the terminals and cable ends with protective grease 

Use a voltmeter to check that the battery is providing enough power. Some outboards require a minimum of 10.5V to keep them running. When you add on other electronic devices that draw power from batteries, they may need to be charged or replaced unless the battery's voltage is at or close to its maximum. 

Outboard Troubleshooting Tip 3: Check the Exhaust

If the exhaust gets blocked, it will cause pressure to build up in the engine and prevent it from cranking over. Check for any blockages in the exhaust and remove them.

Outboard Troubleshooting Tip 4: Check the Fuel

Once you're sure the outboard is getting electricity, the next thing to check is whether it's getting any fuel. 

Outboard won't start troubleshooting fuel pump prime

Make sure the outboard is fully primed with fuel. If the fuel pump isn't primed, the motor may turn over without starting. Squeeze the primer bulb a couple of times to prime the fuel pump. If the primer bulb squeezes easily and doesn't feel like it's pumping fuel, it's time to determine what is preventing fuel from getting to the motor.

Never assume the fuel gauge is accurate, especially for portable and topside fuel tanks on smaller boats. Double-check that there's actually fuel in the tank. When using a topside or portable tank, also check that the tank's vent is open. 

A closed vent creates a vacuum effect within the tank, which prevents fuel from flowing to the engine. If the boat uses a permanent below-deck fuel tank, check that the fuel flow valve is open. A closed valve will prevent any fuel from flowing to the engine. Examine the fuel lines for twists or kinks that may be preventing fuel from flowing properly. Also, make sure the fuel lines are securely attached, and look for any leaks from the connections as you squeeze the priming bulb.

Outboard Troubleshooting Tip 5: Check the Electrical System

If the battery has a charge but none of the helm gauges move when the ignition switch is turned on, it's an indication of a problem in the electrical system. Check all the fuses and replace any that are burnt out. The fuse box is usually located under the helm console, but don't forget to check the engine's main fuse under the outboard's cowling. 

Outboard won't start troubleshooting check fuses

Make sure the spark plug cables are firmly connected, and inspect the leads for any splits or tears in their outer jackets. A split cable jacket may cause a cable to short, so replace any split leads or wrap them in electrical tape as a short-term emergency fix. 

Check to see that the spark plugs are getting electricity and are generating sparks:

  • Remove a plug
  • Reconnect the plug cable
  • Hold the plug against the engine block to ground it. 

When the engine is cranked, there should be a blue spark at the tip of the plug. 

NOTE: Always use a glove or a rag to hold the plug to avoid a painful electric shock.

Check the spark plugs' gaps with a gap gauge, and clean them with a wire brush. The head of a spark plug needs to be relatively free of carbon and set at the correct gap to generate a spark. If the battery has a charge and the spark plugs are working, the emergency kill switch may have failed. Disconnect and bypass the kill switch, and try starting the motor.

Outboard Troubleshooting Tip 6: Check the Engine

For an outboard to fire up, the fuel and air must be compressed before they're ignited by the spark plug within the combustion chamber. Remove a plug and use a compression gauge to test the engine block’s compression. If the motor is lacking compression, there’s no easy fix and you’ll probably have to take it to a mechanic.

If the engine is not cranking over but there’s a small clicking sound when you turn the ignition switch, the starter motor may be faulty. The clicking is the sound of the solenoid trying to get the starter motor to engage.

Gently tap the starter motor a couple of times with a hammer. As the starter motors get older, the electrical brushes inside it become worn. The tapping helps free the worn brushes, allowing them to make an electrical contact and work again.

Outboard troubleshooting starter motor

If the engine is not cranking over and there's no clicking sound when you turn the ignition switch, the solenoid could be at fault.

Put a voltmeter on the solenoid's terminals and crank the engine. 

  • If the voltmeter registers 12V (assuming the engine is running on a 12V battery), then the solenoid is receiving the correct current and is not working properly.
  • If the solenoid is not receiving the correct (or any) current, the problem is probably battery- or cable-related.

The motor may be overheated if it had been running before it cut out. 

  • If the motor is hot when you touch the cowling, check to see if water is coming from the tell-tale nozzle when the motor is cranked over. 
  • If no water is coming out, then the water intake may be blocked and the engine is not getting enough water to keep it cool. Unblock the intake, and allow engine to cool before restarting it.

Be Prepared

Always carry a small collection of tools on board. When a problem arises, they'll be worth their weight in gold! You don’t need a massive mechanic’s tool chest on board with you, but a few essential tools such as an adjustable wrench and a couple of screwdrivers will come in handy when unexpected problems happen (and yes, they do happen).




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