What To Do If Your Boat Engine
Won't Start

Paul Luisi
by Paul
Luisi

Whether it is an outboard motor or an inboard motor, there are many reasons a boat engine may not crank and start.

Figuring out what the problem is that is causing the engine issues involves following a number of troubleshooting steps that should hopefully fix your issues and help to get your boat motor running smoothly again.

If the engine won't start, do not keep cranking the ignition as you may drain the battery.

To get the boat engine to start again, follow the steps:

  1. Make Sure The Key Is Properly Inserted
  2. Check To See Whether The Boat Is In Neutral Or Not
  3. Ensure Boat Engine Safety Features Are Connected
  4. Check To See If The Gas Tank Is Empty
  5. Check To See If There Is Dirt Or Water In The Fuel Tank
  6. Check The Battery Cables & The Battery Itself
  7. Check For Loose Or Clogged Fuel Lines
  8. Check The Fuel Filters For Damage Or Clogged Dirt
  9. Check The Exhaust & Air Vents To See If They Are Blocked Or Damaged
  10. Ensure The Engine Is Primed
  11. Check The Fuses
  12. Assess The Spark Plugs
  13. Check The Ignition Coil
  14. Check The Distributor Cap Or Rotor
  15. Check The Boats Electrical Wires
  16. Check For Loose Or Damaged Ignition Points
  17. Assess The Choke For Damage
  18. Assess The Reed Valves For Damage
  19. Check The Carburetor For Damage Or Clogging
  20. Check The Engine Compression

Marine engines may differ from one brand to another but these steps of what to do should help the majority of vessel owners struggling to get their boats to start.

Hopefully one of these steps will offer the solution to getting the engine running again.

If you've followed these steps and the engine is still not starting, it's time to call a boat mechanic to come and take a look at the engine.

1. Make Sure The Key Is Properly Inserted

Make sure the boat key is inserted properly
Is The Boat Key Inserted Properly?

A very basic first step is to make sure that the boat key to start the engine is inserted properly.

Sometimes dirt can prevent the key from inserting the full way into the ignition and this may be a very simple step that will help fix the issue.

What To Do If The Boat Key Is Not Inserted Properly?

If a boat key is not inserted properly, simply push the key into the ignition until it is inserted properly.

If the key will not insert the full length into the ignition, this may mean there is dirt or something blocking the key from fully inserting into the ignition or that the key or ignition is damaged.

This may mean you will need to use a spare key to help start the boat engine.

2. Check To See Whether The Boat Is In Neutral Or Not

Is Your Boat In Neutral Gear
Is Your Boat In Neutral?

If your boat motor won't start, check to see if the boat gear shift is in neutral and not in gear.

Most boats require a boat to be in neutral gear before it will start. This is a safety feature.

What To Do If The Boat Is Not In A Neutral Gear?

If a boat is not in neutral, simply place the gear stick into the middle position to ensure it is not in the forward or reverse position.

Most boats will label the middle position as "neutral" and it is in the position between forward and reverse.

Placing the boat gear stick in the middle position will ensure the boat is in neutral gear and it may be a reason to help get the boat motor to start again.

3. Ensure Boat Engine Safety Features Are Connected

Ensure the boat engine safety features are connected
Are The Boat Safety Features Connected?

If your boat engine won't start, one reason might be that the safety features that help start a boat may be disconnected.

One common safety feature issue that may be preventing your boat engine from starting is the safety lanyard and kill switch is disconnected.

What To Do If The Safety Features Are Disconnected?

To ensure the safety features are connected to help start a boat engine:

  • Ensure the safety lanyard is connected properly: Make sure that the safety lanyard cable is properly connected. Sometimes it can look like it is connected properly but it is not so please be aware of this. Double-check to ensure the safety lanyard is properly attached
  • Ensure the kill switch knob is engaged (where applicable): Even if the safety lanyard is connected properly, there may need to be a kill switch knob engaged to start the motor that you may have forgotten to do (applicable on certain boats)

A common issue preventing a boat engine from starting is boaters may have their safety lanyard connected but they forget to ensure the kill switch knob is engaged.

4. Check To See If The Gas Tank Is Empty

Manually check the fuel tank

Another issue that may prevent a boat engine from starting is when the fuel tank may be empty.

Even if the fuel gauge indicates that the fuel tank is not empty, a boat owner should manually check the tank as the fuel gauge may be faulty.

What To Do If The Gas Tank Is Empty?

If the gas tank is empty, simply fill up the tank with fuel and that should fix the problem of the engine not starting.

If the gas tank is empty but the fuel gauge signals that there is fuel in the tank, then you will need to fix the fuel gauge faults first so that the problem doesn't arise in the future.

5. Check To See If There Is Dirt Or Water In The Fuel Tank

check for dirt or water in the fuel tank
Is There Dirt Or Water In The Fuel Tank?

If the boat motor is not starting, check the fuel tank to see if there is water or a dirt build-up in the tank.

Water or dirt build-up is a common reason a boat engine may not start.

What To Do If There Is Dirt Or Water In The Fuel Tank?

In order to remove the dirt or water from the gas tank and help the engine to start again, a boater should: 

  • Remove the fuel from the tank: A boat owner should remove the fuel from the tank so that it is completely empty
  • Thoroughly clean the fuel tank: A boat owner should then thoroughly clean the fuel tank so there is no dirt or water left in it
  • Fill the tank with new clean fuel: Once the bad dirt and bad fuel is removed and the tank is cleaned, fill the tank with new clean fuel

Doing this should fix the problem of dirty fuel in the tank and it should assist in getting the boat engine operating again.

6. Check The Battery Cables & The Battery Itself

Check the battery and the battery wires
Is the battery functional?

Another issue that may be preventing your boat engine from starting is when the battery is not functioning properly.

A boat owner should check the battery and the battery cables and wiring to ensure they are operating as normal.

Use a voltmeter to check the voltage of the battery to ensure it is working.

Some boats have a battery switch that should be turned to the "on" position when the boat is in use.

Another tip is on boats that have two or more batteries, one battery may be used to power the electronics on the boat while the other is used for the engine.

This can cause confusion for boat owners who mistakenly believe there is no issue with the battery if they have electrical power when in reality one battery that powers the electronics may be working fine whilst the engine battery may not.

What To Do If The Battery Is Dead Or The Battery Cables Are Damaged?

In order to fix a dead engine battery or damaged battery cables and get the boat engine running again, a boat owner should: 

  • Charge the battery: If the battery is dead, charge the battery until it is working again
  • Replace the battery: If charging does not work, replace the battery with a new one
  • Reconnect loose battery cables: If the battery cables are disconnected, reconnect them
  • Replace damaged battery cables: If a battery cable is damaged beyond repair, replace them with new battery cables

Fixing any fuel line issues should help get the marine engine started again.

7. Check For Loose Or Clogged Fuel Lines

Check the fuel lines
Are the fuel lines connected and functional?

Another reason a marine engine may not start is because of a problem with the fuel lines connecting the fuel to the engine.

If these fuel lines are damaged, clogged, knotted or pinched, it can prevent the fuel from flowing to the marine engine and this can prevent an engine from starting.

Rough weather conditions when out boating can cause problems with the fuel lines getting disconnected or sea water and dirt getting into the lines and clogging it up.

What To Do If The Fuel Lines Are Damaged/Clogged?

To fix any fuel line issues that may be preventing an engine from running, a boat owner should: 

  • Remove the fuel lines and unclog them: Use special cleaning fluid to unclog any clogged fuel lines that may be blocking the fuel from getting to the engine
  • Reconnect any disconnected fuel lines: If the fuel lines have disconnected, reconnect them. Also, ensure the fuel line couplings and connectors are functional and not damaged and are tightly sealed to prevent air from getting into the line
  • Replace any damaged fuel lines: Replace any fuel line that is damaged with a new one
  • Replace any damaged seals: If the seals connecting the fuel line to the engine are damaged or leaking fluid, replace them with new seals to prevent and leakage or further damage

8. Check To See If Fuel Filters Are Clogged Or Damaged

Check the fuel filters
Is the fuel filter damaged or clogged?

Check the fuel filters on the boat engine to see what condition they are in.

Damaged, clogged or dirty fuel filters can cause the marine engine to struggle to start and this may be the reason you're having difficulty in starting your boat motor.

What To Do If The Fuel Filters Are Clogged Or Damaged?

To fix a clogged or damaged fuel filter and get a marine engine started again, a boat owner should: 

  • Clean dirty and clogged fuel filters: Wash and clean clogged and dirty fuel filters to free them from dirt
  • Replace damaged fuel filters: If the fuel filter is damaged, replace it with new ones

Once the fuel filters issue is resolved, it should hopefully help you to get your boat engine running again.

9. Check The Exhaust & Air Vents To See If They Are Blocked Or Damaged

check the exhaust and air vent for clogging
Is the air vent or exhaust blocked?

Check the exhaust and the air vents around the fuel tank to see if they are blocked or damaged.

A damaged or clogged boat exhaust or air vent can be the reason a marine motor might not start.

This problem is very common when a boat is taken out to use after a long period in storage.

What To Do With A Damaged Or Clogged Exhaust Or Air Vent?

In order to fix a damaged or clogged exhaust or air vent, a boat owner should: 

  • Use a bristled brush and cleaning fluid: Use a strong bristle brush to clear out and unclog blocked air vents or exhausts
  • Replace damaged exhaust with a new one: If the exhaust is damaged badly, you will need to replace it with a new one and this can be costly
  • If there is minor damage, repair it yourself: If there is minor damage on an air vent or exhaust, you may be able to fix the problem yourself without needing to spend a lot of money

10. Ensure The Marine Engine Is Primed

Ensure the boat engine primed
Is the boat engine primed?

Another reason a boat motor might not start is because the boat owner tries to start the vessel before priming the engine properly.

Some models of boats require different start up procedures.  Some boats may require turning on an "on" switch and waiting for it to power up.

In other instances, there may be an issue with the primer being damaged.

What To Do If You Cannot Prime The Marine Engine?

In order to fix a boat engine not priming issue and get the boat motor to start again, a boater shoulder: 

  • Remove a fuel hose that connects the primer to the engine on a boat with an electric primer: On boats with an electric primer, remove one of the fuel hoses, get a bucket, place the fuel hose into the bucket and push the key into the ignition to see will the fuel pump into the bucket. If it does, there is not an issue with the electric primer but if it does not, there may be an issue with the electric primer and it will need to be repaired
  • For pressurized fuel systems, pump the primer bulb: For boats with pressurized fuel systems, pump the primer bulb a couple of times. If the bulb becomes firm, everything should be working fine and the fuel system is pressurized but if it does not become firm, there may be a problem. Check the engine, fuel tank etc. for leaks that may be causing the lack of pressurization. Alternatively, the primer bulb itself might be damaged and will need to be replaced

Once the primer issues are resolved, the boat engine should hopefully start up and start operating properly again.

11. Check The Fuses

Check the boat fuses for damage
Are the boat fuses damaged?

A boat motor may not be starting because there is a damaged fuse or a damaged fuse box/fuse wiring. 

This is another common reason for a boat motor to not crank and start.

On an outboard boat, typically you will find the fuse box under the helm and on an inboard boat, the fuse box is typically found in the engine compartment.

In the fuse box, check for a blown fuse (especially ignition fuses) or any damage to the wiring or the box itself.

In inboard engines, there is typically a red switch and yellow reset button that can be the source of problems too.

What To Do If There Is Damage To A Fuse?

In order to fix a damaged fuse or fuse box and get the boat engine started again, a boater will need to: 

  • Replace a blown fuse: If there is a blown fuse, a boater will simply need to replace that with a new fuse and that should suffice
  • Replace the fuse box: If there is damage to an entire fuse box and the wiring, a boater will need to replace it with a new fuse box and wiring to ensure everything is operational again

Replacing a blown fuse is a simple fix that should get your boat motor running again.

A damaged fuse box is more complex to fix but once repaired, the boat engine should operate smoothly again.

12. Assess The Spark Plugs

Check the spark plugs for damage
Are the spark plugs damaged?

If the spark plugs are dirty, damaged or not gapped properly, it can cause a marine engine to not start.

This is generally the most common problem if an engine was running poorly in the past and eventually stopped starting as it may be a sign that the spark plugs need to be replaced.

What To Do If There Is Damage To A Spark Plug?

In order to fix damaged or dirty spark plugs to help get the boat engine started again, a boater should: 

  • Replace the spark plugs: If the spark plugs are damaged, replace them with new spark plugs
  • Clean the spark plugs: If the spark plugs are dirty, clean them and the unit they are housed in to ensure no more dirt is present
  • Adjust the gap between the spark plugs: If the spark plugs are improperly gapped, adjust the spark plugs to the correct gap in order to get them operating properly again

Replacing damaged spark plugs or adjusting the gap should help solve any spark plug issues on a boat engine and help to get the boat started again.

13. Check The Ignition Coil

Check the ignition coil
Is the ignition coil damaged?

If the ignition coil is worn or damaged, it can cause the boat motor not to start.

The ignition coil can also overheat after frequent boat use which can cause it to get damaged.

To test if the ignition coil is damaged, disconnect the wire going into the coil, in particular, the ignition module wire and use multimeter leads to test and get a circuit reading.

If there is no reading, this indicates the ignition coil might be damaged.

What To Do If The Ignition Coil Is Damaged?

In order to fix a damaged ignition coil and get the boat engine started again, a boater should: 

  • Remove any dirt that may be blocking the connection: Remove any dirt that may have become trapped in the wiring of the ignition coil
  • Replace the ignition coil: If the ignition coil is damaged beyond repair, it will need to be replaced with a new coil

Once the ignition coil is operational again, it should solve the problem as to why your boat engine is not starting.

14. Check The Distributor Cap Or Rotor

check the distributor cap
Is the distributor cap damaged?

A damaged distributor cap or rotor can cause the marine motor to not start.

A distributor cap is an important part of a boat's ignition system. It works in conjunction with a rotor and helps transfer electrical charge form the ignition coil to the spark plugs.

This creates the spark needed to ignite the fuel.

To check if the distributor cap or rotor is damaged, remove the cap and rotor and then connect the multimeter to the positive and negative terminals.

Set the multimeter to OHMS mode and check the reading.

What To Do If The Distributor Cap Or Rotor Is Damaged?

If the distributor cap or rotor is damaged, you will need to replace it in order to get the boat engine working smoothly again.

Replacing it can be done by a mechanic or by yourself if you are good at DIY.

15. Check The Boats Electrical Wires

check the electrical wires
Are the electrical wires damaged?

Damaged electrical wires or the wiring insulation can cause the boat motor to not start.

Check the boat's electrical systems for damage or signs of being worn down.

If there is damage to the cables, this could be the problem with the engine not running.

What To Do If The Electrical Wires Are Damaged?

To fix the electrical wires and get the boat started again, a boat owner should: 

  • Repair any damaged electrical insulation: If the insulation is worn down, electrical tape may suffice in fixing any issues
  • Replace damaged electrical wires: Replace any damaged electrical wiring, especially if it is connected to the functioning of your engine

Once electrical wires are damaged, fixing them may be the solution to getting the boat motor up and running again.

16. Check For Loose Or Damaged Ignition Points

Check the ignition points for damage
Are the ignition points damaged?

Damaged or improperly gapped ignition points can cause the engine of a boat to not start.

Perform a visual check of the ignition points structure in the boat's ignition system to see if there is a problem with the ignition points gap.

If they are dirty and not gapped correctly, the engine may not run properly.

What To Do If The Ignition Points Are Damaged?

To fix the ignition points and get the boat started again, a boat owner should: 

  • Adjust ignition points to the correct gap: Adjust the ignition points to the correct gaps to ensure they are operating correctly
  • Replace damaged ignition points with new ones: If the ignition points are damaged beyond repair, replace them with a new one
  • Remove dirt trapped in the gaps: If there is dirt trapped in the ignition point gaps, remove it and ensure it is clean

Once the ignition points are fixed, it should hopefully help you to get the boat motor started again.

17. Assess The Choke For Damage

check to see if the manual choke is damaged
Is the manual choke damaged?

If your boat has a manual choke, the linkage may be bent or damaged.

This can prevent your vessel's engine from starting if the choke is not functional.

What To Do If The Manual Choke Is Damaged?

To fix a manual choke and get the boat engine started again, you should: 

  • Repair a bent choke linkage: If the choke linkage is bent, you can use a hammer to adjust it back to its rightful position
  • Replace a damaged choke linkage: If the choke linkage is damaged structurally beyond repair, you will need to replace it with a new one

Once the choke linkage is sorted, this should hopefully help get the boat motor to start and run again.

18. Assess The Reed Valves For Damage

check the reed valves for damage
Are the reed valves damaged?

A boat engine's reed valves help control the airflow to the engine. They are typically located below the carburetor on two-stroke engines.

If they are cracked, leaking, have a build-up of dirt or are damaged in any way, they may stop functioning properly and cause the engine to not start.

Any holes or cracks in the reed valve can cause air and fuel to leak out of the engine and not get compressed properly.

What To Do If The Reed Valves Are Damaged?

To fix reed valve issues and get the boat engine started again, you should: 

  • Remove any trapped dirt: If there is trapped dirt in the valve, clean and remove it to prevent any loss in functionality
  • Reseal any unsealed reed valve: If the reed valve becomes unsealed, reseal it with a special product to help reseal it
  • Replace damaged reed valves: Replace any damaged beyond repair reed valves with new ones

Once the reed valves are repaired or replaced, it should help the airflow and fix the issue with a boat motor not starting.

19. Check The Carburetor For Damage Or Clogging

Check the carburetor
Is the carburetor clogged or damaged?

A boat's carburetor supplies the boat engine with air and fuel mix. If this is clogged, cracked, leaking or damaged, it can cause the marine engine to not start.

What To Do If The Carburetor Is Clogged Or Damaged?

To fix a clogged or damaged carburetor and get your boat engine started again, a boat owner should: 

  • Clean the dirt to remove the clogging: Thoroughly clean the carburetor to unclog it and ensure there is no dirt left after the clean
  • Ensure they are adjusted correctly: Ensure the carburetor is adjusted correctly to provide the correct air and fuel mixture. If it is not already adjusted correctly, do it yourself or get a mechanic to adjust it
  • Repair or replace damaged carburetor: If the carburetor is cracked or damaged, fix the crack or replace the carburetor if it is severely damaged

Ensuring the carburetor is fixed should assist in getting the engine back up and running again.

20. Check The Engine Compression

Check the engine compression
Is the engine compression low?

If the boat engine has low compression, it means that the cylinders are unable to compress enough air.

This can be a reason for your boat engine to not start.

A low compression engine can signal serious engine damage like a blown head gasket.

To test a boat engine compression, you will need an engine compression tester kit.

What To Do If The Boat Engine Compression Is Low?

To fix a boat engine compression issue and get your boat engine started again, a boat owner should: 

  • Assess what may be causing the low compression: Is it a blown gasket or something else? This will determine what fixes need to be made
  • Contact a mechanic: As this is complicated, it's best to contact a mechanic if the engine has low compression as finding a solution may be difficult for someone untrained

A low compression engine is one of the more difficult problems to solve to get the engine up and running again.

Summary

Hopefully, one of these steps listed will help solve your engine issues.

These problems and solutions are applicable to most boat engine brands including Volvo, Mercury, IImor, Yamaha, Honda, Suzuki etc.

As a tip, do not make drastic changes if you are unsure about how to fix a problem.

Instead, hire a professional boat mechanic to fix the engine if you are not confident in your own abilities.