Outboard boat motor won't start

Symptoms

• Motor cranks but won't fire
• Motor doesn't crank at all
• Motor started fine last time out but not now

Likely causes

• CommonSafety lanyard/kill switch not attachedMost outboards won't start at all without the kill switch clip in place, which is easy to forget.
• CommonDead or weak batteryMarine batteries can discharge from sitting, parasitic draws, or simple age, similar to any battery.
• CommonStale fuel or a fuel line not primedEthanol fuel degrades faster in marine use, and the primer bulb needs to be squeezed firmly before starting, especially after sitting.
• PossibleFuel/air mixture issue from a dirty carburetor after storageSimilar to small engines and motorcycles, varnish buildup after storage can prevent reliable starting.

What to do

1. Confirm the safety lanyard/kill switch clip is properly attached, since this is one of the most common overlooked causes.
2. Check the battery connections and charge; jump or charge it if it's weak, similar to a car battery.
3. Squeeze the primer bulb on the fuel line firmly until it feels hard, which indicates fuel has reached the carburetor or injectors.
4. Check the fuel itself; if it's more than a season old without stabilizer, consider it a likely contributing cause, especially if the motor is hard to start or runs rough briefly then dies.
5. Check that the fuel tank vent is open, since a closed vent can prevent fuel from flowing properly.
6. If the motor still won't start after these checks, and especially if it sat with old fuel over winter, the carburetor may need cleaning by a marine mechanic.

Tools and parts

• Basic hand tools

When to call a pro

If basic checks don't get it running, especially after winter storage, a marine mechanic can service the carburetor and fuel system.

Safety