Boating Basics Online is reader-supported. When you buy via our links, we may earn a commission at no cost to you. Learn more

12 Reasons Why My Boat Engine Won’t Start & How to Fix

Written by J. Harvey / Fact checked by S. Numbers

reasons why my boat engine won't start

An unresponsive vehicle motor is a problem, especially out at sea. You may be asking “what are the reasons why my boat engine won’t start?” and it’s best to learn more about these as soon as possible.

The cause can be simple, such as running out of gas, to more complicated ones such as a specific component being broken and needing replacement. Let’s look at some of the most common ones and how they can be addressed.

Common Reasons Why Boat Engines Won’t Start

Whether you’re using an inboard boat motor or a 2 stroke outboard motor, some problems can arise. Fortunately, many can be fixed with quick and easy solutions.

When a boat motor wont start, it may actually be a simple problem or an overlooked detail. It helps to know what to look at.

Here are several common causes and a brief description of how to fix them.

1. Disconnected lanyard or safety switch

Having a safety lanyard is essential because it kills the motor should the operator be thrown overboard. The lanyard pulls the kill switch, which disrupts operation as an emergency measure. But when left disconnected, it will prevent the boat from starting.

If the boat motor stopped suddenly, it is also possible that the safety switch was disconnected by accident.

How to fix: Reconnect the safety lanyard or switch.

2. Gear not in neutral


Another problem that seems simple but could happen to anyone is having the gear anywhere other than neutral. If your outboard motor won’t start after running just a while ago, this is another thing to check.

How to fix: Simply shift your gear back to neutral to address this problem.

3. Dead battery

This is one of the most common inboard boat engine problems that you should not expect outboards to be exempt from; there may not be enough charge; the battery could be flatlined, or even dead. Any one of these means you won’t be able to start the engine unless the concern has been addressed.

A possible symptom of this is when the boat won’t start no click.

How to fix: Batteries need to have 12.6 volts of charge; measure it with a voltmeter to check. If the battery is low on power and the boat won’t turn over, charging should fix the problem. If it does not charge, it may be dead and needs to be replaced.

4. Fuel on empty


An empty fuel tank means you won’t be going anywhere. While this seems like a silly reason for the vessel to stop working, it could happen to anyone.

What’s worse is if this happens while in the middle of a trip. You may have miscalculated your fuel consumption or forgotten to refuel before departing.

How to fix: The obvious solution is to fill up on gas, but this is easier said than done if you’re away from the dock. It’s a good idea to always have some spare fuel on board.

5. The engine is not primed

Engines may require a bit of warmup to start properly. The time needed to prime each engine can be different. The priming method may also differ from one boat to another as some use an electric primer instead.

How to fix: Refer to your manual and check for the proper way to prime your boat. Basically, you must turn the key to the “on” position and wait for the engine to fire.

If your primer bulb doesn’t draw fuel, try mounting it vertically instead of horizontally. The bulb may also be broken and needs replacing.

6. Improper startup sequence


Another problem that may arise if you are not used to the vessel you’re operating is making a mistake in its startup sequence. For example, you need to ensure the kill switch is ‘on’ before starting the engine.

How to fix: Refer to your user manual for the proper sequence. Some vessels also have knobs or switches that are hard to turn. Boats taken out of storage after winter may also be more difficult to start up.

7. Exhaust or vent blockage

An issue that may arise for a boat after sitting in storage for a long time is having blocked exhaust vents. There are a lot of things that can cause this blockage, including dust buildup, debris, and small creatures like insects, rats, or even birds.

How to fix: Clear the vents and exhaust opening of any blockage, enough to allow the air to flow freely to address this concern. This problem is also common after winter, so do some thorough cleaning after getting the craft out of storage.

8. Contaminated fuel system


The engine fuel system is sensitive to foreign materials, and any sand or debris that gets into it will create issues that may prevent you from working the vessel. Water could also build up during or after winter, and any that mixes into the fuel will prevent combustion, keeping your engine from starting.

Dirty fuel filters are also a concern.

How to fix: Replace the filters. If the fuel looks contaminated, it will be necessary to drain it out and replace it with a new supply. Make sure to replace your filter regularly to avoid the buildup of unwanted substances.

9. Spark plugs

The spark plug is responsible for starting the engine by taking electricity from the battery and igniting the fuel to create combustion. If your boat engine cranks but wont start or is slow to crank, it may mean that the spark plug is misaligned or dirty.

There is also the possibility that it is worn or damaged.

How to fix: If you know where to find the spark plug, clean and adjust it using a feeler gauge and gap tool. However, even if you get it to work, it’s still a good idea to examine it for damage and possibly replace it in case of wear.

10. Bad starter


If you hear a buzzing or grinding sound when starting the boat, this is an indicator that there may be a problem with the starter. It is also possible that the motor will not start, no cranking or anything.

How to fix: Replace the starter. Wire connections may also need to be checked and cleaned.

11. Loose or obstructed connections

When the boat engine won’t turn over battery good, it means that there may be a problem with your electrical wires, such as if the starter is not getting the power it needs from the battery. If the engine on boat turns over but won’t start, it may have something to do with the fuel connections.

To fix: All wires and connections need to be secured properly, but it may be difficult to find the specific concern if you’re not familiar with the system. Call for professional help if you’re not sure about how to approach it; this is a problem that can be prevented by going through routine checkups.

12. Mechanical failure


A marine engine has many parts, and a problem with any one of these (e.g. bent choke linkage, damaged reed valves) may lead to operational difficulties, possibly even keeping the engine from starting up at all. There is also the possibility that there is no damage, but the settings for components such as the carburetor are not properly adjusted.

How to fix: If you are not well-versed with the engine and its components, your best bet is to call for someone qualified to fix the malfunction. However, preventive maintenance is important for this as well. Make sure that you go through periodic checks regularly to limit the occurrence of these types of problems.

Frequently Asked Questions


How do you start a boat that won’t start?

There are many causes for a marine engine that won’t start, and it helps to observe the details. A boat cranking but not starting could mean a problem related to fuel, while having clicking and no cranking could mean something is wrong with the battery.

Make a list of the things you can do and check them based on the symptoms you’re observing. Hopefully, you’ll be able to identify the source and fix it. If not, you will have to call for a professional.

Should I hear a click when starting the boat?

No, you don’t always hear the click. This click is the sound of two starter components making contact; however, the instant that the connection is made is also when the engine starts turning over, resulting in the clicking sound being overlapped.

This means that it is normal that the boat turns over but won’t click; it is not that it does not click but that you just don’t hear it.


After asking “what are the reasons why my boat engine won’t start?” now you know about several of the usual causes and ideas on how to fix them. Even if it’s a top-of-the-line Mercury outboard, machines break down sometimes, so be sure to take good care of them.

Learning about all this is difficult, so take your time to familiarize yourself. Whether your boat engine turns over but wont start or it stops suddenly, there’s always a solution to treat the problem.

Remember to boat safely.

5/5 - (2 votes)