Engine Clicks but Won't Crank - Testing the Battery, Cables, Neutral Switch, Solenoid and Starter

Salt Water Sportsman lists these first, and they solve a surprising number of no-crank days:

• Battery switch turned ON (or to the correct battery).
• Shift lever in neutral. Try moving it firmly to neutral, or jiggling it in neutral while turning the key.
• Kill switch lanyard clipped on, on engines where it affects starting.
• Fuses on the engine, at the helm and in the battery area. Know where they are before you need them.

Set the meter to DC volts and put the probes on the battery posts themselves, not on the cable clamps.

• At rest: a fully charged 12-volt battery reads about 12.6 volts or a bit more.
• While a helper turns the key to START: SAIL Magazine's Nigel Calder explains that a healthy battery dips to around 12 volts and then slowly declines while cranking.
• Voltage crashes: the battery is discharged or worn out, or (rarely) the starter has a dead short. Charge it fully and test again; if it crashes again, replace it. Yamaha recommends a load test if you have any doubt, which any auto parts store can do.
• Voltage doesn't change at all and nothing turns: the current isn't flowing. Look at the switch, solenoid and starter (steps 6 to 9).
• Voltage dips but doesn't crash, and the engine turns slowly or not at all: there is too much resistance somewhere. Do the voltage-drop tests in steps 4 and 5.

A good resting voltage alone does not prove the battery is good. It must hold up under load.

Turn the battery switch off. Disconnect the negative cable first and reconnect it last. Then take apart and clean:

• Both battery terminals and cable ends
• The battery switch terminals
• The positive cable at the solenoid and starter
• The engine ground (where the negative cable bolts to the engine block or powerhead)

Yamaha warns that a terminal can be corroded yet look clean, and that corrosion can rot the copper strands inside a wire's insulation. Clean both faces to bare, shiny metal, refit with hex nuts and lock washers (not wing nuts), tighten, and coat with a corrosion inhibitor. Salt Water Sportsman notes that a click when you turn the key often points to a loose battery connection, and the fix is to wire-brush the terminals even if they look clean.

Voltage-drop tests find bad connections that you can't see. Calder points out that with the meter on volts, it's very hard to damage the meter or yourself, and that the readings only mean something while the starter is cranking.

• Put one probe on the negative battery post and the other on clean bare metal on the engine block (scratch a little to make good contact).
• Have a helper crank the engine.
• The reading should be well under 1 volt. Higher means resistance in the ground path.

Calder says the most common trouble spot is where the negative cable bolts to the engine, followed by the battery post connection. After a failed test, feel the cables and connections (carefully): warmth means resistance. Clean that joint to bare metal and test again.

• Put one probe on the positive battery post and the other on the big positive stud on the starter (where the heavy cable or strap from the solenoid attaches).
• Crank. Again, the drop should be well under 1 volt.
• If it's high, narrow it down by measuring across each part while cranking:
  • Across the two big terminals of the solenoid: Calder says anything more than a tenth or two of a volt means the solenoid contacts need attention. In SAIL's Ask Sail column, he says the reading should be at most a few tenths, certainly no more than 0.5 volt.
  • Across the battery switch's main terminals: again no more than a tenth or two of a volt. Calder suggests turning the switch on and off a dozen times and retesting, since that can clean the contacts; if it stays high, replace the switch.
  • Across each cable, end to end, and across any fuse in the circuit.

Long cable runs on boats are often undersized. If a cable gets warm while cranking, it may need to be replaced with a heavier one.

If the solenoid doesn't click at all, find the small wire on the solenoid (the "start" or "S" terminal). Put the red probe on it and the black probe on clean engine ground, and have a helper turn the key to START.

• Close to battery voltage, but no click: the solenoid's coil has failed, or the solenoid isn't grounded (some ground through their mounting bracket). Clean the mount and retest before replacing it.
• Little or no voltage: the problem is upstream, in the key switch, neutral safety switch, start relay, fuse, or a corroded harness plug.

Calder also describes an intermittent version: on some engines, undersized wiring between the key switch and the solenoid drops the voltage so much that the solenoid drops out, so the engine cranks some days and not others. The fix is better wiring or an added relay, installed by someone who knows marine wiring.

The neutral safety switch only lets the engine crank in neutral, so you can't start in gear. On outboards and sterndrives it is usually in the remote control box or on the engine's shift linkage. A worn control, a stretched or misadjusted shift cable, or corrosion can keep it from closing even when the lever looks like it's in neutral.

• Move the lever firmly into neutral and try again.
• With a meter, a technician can check whether the switch passes voltage in neutral and blocks it in gear.
• If the shift cable needs adjusting, see the shift-cable-adjustment and remote-control-box-service guides.

Never bypass the neutral safety switch to get going. Starting in gear can throw people overboard or into the propeller.

Many fuel-injected outboards, sterndrives and inboards use a small start relay and a fuse between the key switch and the solenoid. Your owner's manual or the label on the fuse box shows where they are. A blown fuse or a relay with corroded pins stops the click entirely. Replace a fuse only with the same rating; if it blows again, stop and have the wiring checked.

If the battery holds up, the voltage drops are low, the solenoid clicks and full battery voltage reaches the starter's big terminal while cranking, but the starter doesn't spin, the starter motor itself is likely bad (worn brushes, a stuck drive or a seized motor). Calder notes that a starter with a dead short makes battery voltage crash and gives off a distinctive burned smell.

• Starter spins but doesn't turn the engine: the drive gear isn't engaging the flywheel. On an older boat, also confirm the battery cables aren't reversed: a previous owner may have spliced in cables with the wrong colors, and some starters then spin backward and never engage. Trace each cable from the battery post to the engine rather than trusting its color.
• Grinding: worn or damaged teeth on the drive or flywheel.

If the battery was ever connected backward, Mercury's FAQ says to check the engine's fuse or fusible link first and to have a dealer inspect the boat, because reversed polarity can damage the regulator/rectifier, the tachometer, the engine computer and wiring, plus electronics on the boat.

Starter replacement is a job for a pro or an experienced owner with the service manual. On sterndrives and inboards, the starter, solenoid and alternator must be marine ignition-protected parts. Boating Magazine warns that replacing engine-space components with non-marine automotive parts creates an explosion risk.

A single click with the starter unable to move the engine can also mean the engine is locked, often by water in a cylinder from a flooded exhaust, a failed head gasket or a cracked part. SAIL Magazine describes how the starter alone did no harm, but the engine firing on the next attempt bent a connecting rod. So:

• Stop cranking.
• On a gasoline engine, remove the kill clip and the spark plugs and try turning the engine gently by hand (on an outboard, by the flywheel). Water spitting from a plug hole confirms it.
• On a diesel, SAIL's article describes opening the decompression levers (if fitted) and turning the engine by hand; water coming out means it was hydrolocked. The same article explains that repeated cranking of a diesel that won't fire keeps pumping raw water into the exhaust, so close the raw-water seacock if it doesn't start after a couple of tries, and reopen it once it runs.
• If you find water, call a pro quickly. Water left in the cylinders causes rust damage within days (see the water-in-engine-oil and submerged-engine-recovery guides).

Use the safest option first:

1. Dual-battery boats: switch to the other battery or to "Both/Combine," as Salt Water Sportsman suggests, instead of using cables. See the battery-switch-dual-battery guide.
2. Portable jump pack: follow its instructions. Many have an on/off switch; connect both clamps with it off, then switch it on, so any spark doesn't happen at the clamp.
3. Jumper cables from another battery: heavy cables, and only after ventilating.

Before connecting anything on a sterndrive or inboard, run the blower (Boating Magazine recommends four to six minutes) and sniff. If you smell fuel, don't jump. Then:

• Connect red to the dead battery's positive post, then to the good battery's (or pack's) positive.
• Connect black to the good battery's (or pack's) negative.
• Make the last connection to clean, unpainted metal on the dead engine's block (the engine ground), away from the battery and away from fuel lines and the fuel filter.
• Crank in short bursts (about 10 seconds at a time unless your manual says otherwise) with rests between.
• Remove the cables in the reverse order.

Don't "jump" the solenoid with a screwdriver across its terminals. It makes a large spark right at the engine, and on many engines it bypasses the neutral safety switch, so the engine can start in gear.

Once you find the fault, repair it with marine-grade parts: tinned wire, sealed heat-shrink terminals, hex nuts with lock washers, and the solenoid, relay or starter your engine maker specifies. Label wires before you unplug anything. Coat finished connections with a corrosion inhibitor. Then charge the battery fully and do a final cranking test with the voltage-drop readings, and write them down with the date for next time.