Outboard Boat Engine Won't Start: Common Issues and Fixes (2023)

We've all been there - your boat is in the water and packed with guests and gear. You're finally set to take off and go to crank the motor only to find that the boat won't start.Along with a few choice words, your first reaction will probably be something along the lines of "oh great, I wonder how much this is going to cost me".

Don't fret just yet! As with any modern motor, there are simple steps to follow to identify the source of the problem and begin troubleshooting the issue. With any luck and with the help of these common outboard starting fixes, you'll be able to identify and fix the issue in no time and save the day (as well as some money).

Engine Won't Crank or Cranks Slowly

Outboard Boat Engine Won't Start: Common Issues and Fixes (1)

Check the Gauges

If the engine doesn't crank at all, turn the keyto the on position and check to see if other lights and gauges operate correctly. If everything else is dead too, check the outboard's main fuse.

Battery Switch

If your boat has a battery switch, ensure that it's switched to the on position and try again.

Gear Shift

Most outboards will not crank if the boat is in gear. If the engine won't crank but other lights and gauges work correctly, check that the gear shift is in neutral.


If the engine cranks slowly or doesn't crank at all, it's possible your battery may be dead or low. Use a voltmeter to check the condition of your battery. If the voltmeter reads below 12 volts, your batterymost likely is the problem and may need to be jumped or replaced.

Battery Connections

If your battery is holding adequate charge, the cables or connectors may be faulty. Check and clean the battery terminals and connectors to rid them of any corrosion buildup. Inspect the cables for any cracks, corrosion, or other obvious signs of wear that may impact their performance. Once the terminals and connectors have been cleaned and the cables have been inspected, securely attach them back to the battery and see if this solves the issue.

Check Your Starter

If you hear a clicking sound or a low whine when you turn the key, the starter solenoid may be the issue. Before having a mechanic take a closer look, first try the old method of tapping the starter motor lightly with a hammer before turning the key again. This may knock the internal connections back into place allowing them to make better contact. This method may get you out of a bind once or twice, but you should quickly replace the solenoid before its condition worsens and leaves you stranded for good.

Engine Cranks But Won't Start

Outboard Boat Engine Won't Start: Common Issues and Fixes (2)

(Video) My Outboard Won’t Start | Outboard Starting Problems | Diagnosing an Outboard That Won’t Start

Emergency Shutoff

If your boat has an emergency shutoff switch, check that the cap is firmly in place or the engine might not start.

Spark Plugs

If you experience trouble starting the engine, engine hesitation, loss of power, or decreased acceleration, you may have failing spark plugs. Check the spark plugs for signs of damage. Any spark plug that contains moisture or black soot indicates that it is damaged and should be replaced.

Fuel System

This one is obvious, but check that the boat actually has fuel in it. You never know when fuel gauges will fail! If the boat has fuel, check your primer to make sure fuel is making its way to the engine. If your boat has a primer bulb, pump the bulb to ensure it fills with fuel and feels firm after several squeezes. If it doesn't, check for obvious signs of leaks or that the primer bulb itself doesn't have a bad valve. If your boat is equipped with an electric primer, check that it's working properly by removing the hose leading to your intake or carburetor and manually operate the primer to see if fuel squirts out. If it does not, you may need to have your primer serviced.

Exhaust and Compression

If you have run through this checklist and your engine still won't start, you may have either blockages to your exhaust or your engine may be lacking compression. Since these issues may require a more resources and experience than the average boater has, we recommend taking the boat in to a certified mechanic at this point to help troubleshoot the issue.

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Outboard Boat Engine Won't Start: Common Issues and Fixes? ›

If you have checked the battery switch and charged the batteries, but your boat engine still won't start, check the battery cables. Make sure the connections that run between the engine and the battery are not loose or corroded. Reconnect or replace any battery cables that have become disconnected or damaged.

How do you diagnose outboard starting problems? ›

Diagnosing an Outboard That Won't Start - YouTube

How do you start a boat that won't start? ›

Outboard On Your Boat Won't Start? Try These 3 Simple Fixes First!

How do you start a stubborn outboard motor? ›

Five Steps to Starting an Older 2-Stroke Outboard Engine:

Squeeze primer bulb till firm. Advance throttle in neutral to 2/3s. Turn key on, push to choke (or pull out choke) and crank at the same time. Release choke, return the throttle to neutral after ignition.

What would cause a boat motor to stop running? ›

If your boat motor is fuel injected, a dirty or defective airflow sensor can cause poor engine performance. Cleaning or replacing the airflow sensor may clear up your stalling problems. A dirty carburetor can't properly regulate the air and fuel mixture that the engine needs to run which can lead to stalling problems.

What can cause an outboard motor to not start? ›

Common Causes and Solutions for a Boat Engine That Won't Start
  • Safety Features Engaged. ...
  • Starting Sequence Errors. ...
  • Boat Not in Neutral. ...
  • Dead or Disconnected Battery. ...
  • Engine Not Primed. ...
  • Empty Gas Tank. ...
  • Loose or Pinched Fuel Lines. ...
  • Air Vents or Exhaust Blocked.
Aug 2, 2019

What to check on an outboard motor that has been sitting? ›

What Should You Do If An Outboard Has Been Sitting For Awhile? Remove the Spark Plugs & Oil The Cylinders, Replace Plugs if Needed. Check the Condition of the Gear Lube. Disconnect the Fuel Line From the Boat & Check the Condition of the Fuel.

Why is my Mercury outboard not starting? ›

Reason 1: Battery Issue

One of the most common problems that mercury outboard faces are complications of a battery issue. First, check the battery state and make sure it is charged enough to start the engine. If it is charged enough but still not responding, then discharge it. Again recharge it and then try to start.

What is vapor lock on a boat? ›

Vapor lock occurs when liquid fuel turns to vapor before it gets to the carburetor or fuel rail. This is a problem because pumps designed for liquid do not pump vapor very well. Vapor lock causes: Loss of fuel pressure (and flow) Loss of power.

How do you Unflood an outboard motor? ›

To clear, remove plugs, crank engine, or pull starter to expel excess fuel. Clean and dry plugs with cloth. Replace plugs, try to start with max throttle & no choke. If it starts, then dies, you can then try with a little choke as per a normal start.

How do you test an outboard starter? ›

Turn your ignition switch to “Start” and read the voltage. If the reading is more significant than 9.5 volts, try to start the engine. If this test fails, then your boat starter requires replacement or rebuilding. If the reading is less than 9.5 volts, you have a voltage loss between the battery and starter.

How do you test a starter solenoid on an outboard motor? ›

Reattach and secure the battery cables and with the transmission in neutral, rotate the battery selector switch to the "on" position. Turn the ignition key to start. If you hear a clunking noise coming from the starter, it's the solenoid trying to do its job and there is probably nothing wrong with it.

How do you troubleshoot a 2 stroke outboard motor? ›

Outboard motor trouble shooting and maintenance - YouTube

How do you check outboard spark plugs? ›

How to Test Spark Plugs on an Outboard - YouTube


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