Engine Won't Start or Won't Crank - Troubleshooting Guide

The emergency stop lanyard (clip) must be attached to the switch. On many engines it will not even crank without it; on others it cranks but will not fire. Push the clip firmly into place. This is the number one no-start cause.

Most engines will not crank in gear. Move the shift lever firmly into neutral. If it still does not crank, wiggle the lever through neutral while holding the key, because a worn neutral safety switch sometimes needs the lever in an exact spot.

Turn the battery switch to ON (or 1, 2, BOTH). Turn the key to the ON position (not start). Do the gauges, lights and warning beep come on? No power at all points to the battery, battery switch, cables or main fuse.

Measure across the battery posts with a multimeter. A fully charged 12-volt battery reads about 12.6 volts at rest. Below about 12.2 volts it may not crank a large engine. If the starter turns slowly or just clicks, charge the battery or jump it with a jump pack, then have it load tested.

A resting reading alone can fool you. If you can, have a helper turn the key while you watch the meter: a battery that looks fine at rest but drops sharply while cranking is weak, and a load test will confirm it. Auto parts stores and dealers can do one.

Loose or corroded connections cause most "it worked yesterday" problems. Check both ends of the positive and negative battery cables, the battery switch terminals, and the engine ground. Clean to bright metal and tighten firmly. A terminal that looks clean can still be corroded underneath. If your battery posts still use wing nuts, swap them for hex or nylon locking nuts, which do not shake loose.

Check the engine's main fuse and any fuses or circuit breakers in the key switch or helm circuit (see your manual for locations and ratings). Replace a blown fuse only with the same rating; if it blows again, stop and call a pro.

A single click when you turn the key, with a charged battery, often points to the starter solenoid or starter motor. That is usually a shop repair.

Engine cranks but will not fire? Start with the basics:

• Is there fuel in the tank? Gauges can be wrong; check by eye or dipstick if you can.
• Is the fuel valve (if equipped) open?
• Is the portable tank vent open? On a built-in tank, look at the vent fitting on the hull side: Boating Magazine points out that insect nests or wax can partly block it.
• Is the fuel line kinked, and are the quick-connect fittings fully clicked in at the tank and engine?

On outboards, squeeze the primer bulb until it is firm. If it never gets firm, there is an air leak or a bad bulb or fitting. If it collapses and stays flat, the tank vent may be closed or the pickup blocked. Check for fuel drips at every connection; any leak means stop and fix it before cranking.

Also look at the bulb itself. The arrow on it must point toward the engine; a bulb installed backward cannot push fuel. A bulb that has turned hard and stiff, or squeezes but barely pumps, has worn-out internal one-way valves, according to BoatUS, and its old rubber can also crumble into the fuel. Replace it (ideally with a matching fuel line) rather than trying to soften it.

Carbureted engines may need the choke or the primer (push-to-choke key, or fast idle lever) when cold. Fuel-injected engines usually need no throttle: cranking with the throttle open can flood some engines. If you think it is flooded, follow your manual's flooded-start procedure. Check your manual for your engine's exact method.

Look at the water-separating filter bowl or the on-engine filter. Water, rust or gunk means contaminated fuel. Replace the filter. If there is a lot of water, the tank needs to be drained and cleaned; ethanol-blended fuel can absorb water and separate into a layer at the bottom of the tank. A quick check: draw a little fuel into a clear glass jar and let it settle for about half an hour. Clear water or a cloudy layer at the bottom means the fuel is contaminated.

Fuel that sat for months without stabilizer can go stale and gum up carburetors and injectors. Signs include a sour or varnish smell. Fresh fuel from a portable tank connected straight to the engine is a quick test. Old, gummy fuel systems usually need a dealer to clean.

Remove a plug (with the kill switch clip removed so the engine cannot start). A wet, fuel-soaked plug suggests flooding or no spark; black and sooty suggests a rich mixture or weak spark; oily suggests other problems. Replacing old plugs with new, correctly gapped ones is a cheap test. Testing for spark safely requires an inline spark tester; do not hold plug wires by hand.

After winter storage, mouse or bird nests can block the exhaust outlets or air intake, and some owners tape over intakes or the flame arrester when winterizing. Remove anything that does not belong there.

Modern engines store fault codes and may show warnings on the display. If none of the above fixes it, you may have an ignition, sensor or compression problem that needs a dealer's diagnostic tool.