Schedule a demo to enter to win free SeaKits Essentials


What to Do if Your Outboard Won’t Start


This step-by-step troubleshooting checklist will help you pinpoint problems.

While outboards have become more and more complex, they still operate on much the same principles as they did before the current wave of EFI/DFI and four-stroke technology.

To start and run, an outboard needs:

  • Ignition (properly timed)
  • Fuel/air mixture (in the right ratio)
  • Compression
  • Exhaust

Troubleshooting with most newer outboards has become more complicated because of technological advances such as kill switches, start-in-gear protection, electronic ignition and fuel injection, and computer-controlled ignition timing. But this flow chart will help you isolate the problem, so that you may be able to solve it at the dock or ramp with minimal tools in a short amount of time. If not, at least, you’ll be able to speak intelligently about the problem to a mechanic.


With the cover removed from the engine, there may be exposed parts that could harm you. Unless you are confident in what you are doing, leave well enough alone and call for a tow from TowBoatUS.

This is by no means a complete troubleshooting guide for starting problems. Purchase a factory service manual for your year/make/model engine. These are designed for technicians so the information may be hard to understand, but they can be a great aid in helping you diagnose and fix problems, if you’re mechanically inclined and have the temperament to do so.

Lights And Gauges

If you turn the key to crank the engine and nothing happens, keep the key in the “on” (not all the way over to start) position and check to see if other components (such as lights and gauges) operate.

Battery Switch

If your boat has a battery switch, ensure that it’s switched to “on” or “both.”

Gear-Shift Position

If you turn the key and the engine won’t start but other components are working, check the gear shift to ensure it’s solidly in neutral, as most outboards will not crank with the engine in gear.

Emergency Shutoff

Check to see that the ­emergency shutoff switch cap is in place. (Depending on your setup, the engine might not even crank if the kill switch is out.)

Battery Cables

If your battery’s reasonably charged, check the battery cables from the battery to the engine. Often the positive and negative connections loosen over time and/or become corroded.

Low Battery

If the starter engages and cranks slowly or not at all, your battery may be low. Check it using a voltmeter. A minimum of 12 volts is needed.

Main Fuse

Check the outboard’s main fuse. Typically located in a large red holder on the engine wiring harness, it’s usually a 20-amp fuse that’s easily replaced.


If the fuse is OK, check the main power plug that connects the engine wiring to the boat.

Neutral Switch

If it still won’t crank, check the neutral switch. It’s typically inside the control box connected to yellow and yellow/red striped wires.

Starter Solenoid

If you hear a clicking sound or a low whine but the starter won’t engage the flywheel when you turn the key, the starter solenoid may be bad. Some advise against this, but often I’ll tap it lightly with a small hammer as a helper turns the key.

Primer Bulb

Check to see that fuel is getting to the engine. Pump the primer bulb (if equipped) and ensure it gets firm after several squeezes. If it doesn’t, check for leaks in the line, the tank or filter, the engine, and a bad valve within the bulb.


Check filter(s) for water and sediment. One is on the engine. Another may be in line outside of the engine.

Fuel-Line Couplings

Check that fuel line couplings are securely seated and locked.


Check fuel system O-rings. A torn O-ring could introduce air into fuel.

Electric Primer

If the engine has an electric primer, you can usually remove one of the small fuel hoses that goes from it to the engine’s intake or carburetor, and have a helper operate the primer (usually pushing the key in) while you watch to see if fuel squirts out. Avoid letting fuel spill.

Spark Plugs

Try replacing your spark plugs. If that doesn’t help, consider calling a qualified mechanic. The engine may need new coils.


Check the exhaust outlets for blockage. If an engine can’t exhaust the burnt fuel/air mixture, it won’t start. We’ve seen outboards stored for winter that fail to start in spring because large rodent nests caused exhaust blockage that kept the engine from starting.


If the engine is lacking compression, this may be more than you can do at the boat ramp, and it could be time to call in the pros.

John Tiger

Contributor, BoatUS Magazine