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My Engine Will Not Crank Over

If you can crank the engine but it won't start, go HERE.

The number one reason for your engine not cranking is a dead battery. If you are sure your battery is fully charged there are a few more items that you can check.

When you turn on the ignition key do the gauges activate?
If not, it means you are getting no voltage to the dash and/or key switch. This can be a blown ignition fuse, a popped circut breaker, a loose or bad harness plug, a bad ground or even a bad keyswitch.

A good tip is to unplug, inspect and plug back in the main harness plug back at the engine. This is a big black rubber "cannon" plug. The pins in the plug or socket can fail to make contact. Clean up the pins and socket holes. Push the plug firmly back into position but use care not to overtighten the hose clamp. Over tightening the plugs hose clamp will ruin the plug and/or socket.

Your engine has red circut breaker button. It's usually mounted on the same bracket where the harness plug is located or where the starter slave solenoid is mounted. Push in the red breaker button really hard. It's a stiff breaker so push hard. The breaker can pop out if the harness is shorted or overloaded. A bad alternater can also cause a breaker to pop out. You might have to locate the short before using the engine.

Key Switches go bad. It's a moving part and water can get down into the switch. The Mercruiser Key Switch has three terminals on the back. One is a large Red wire which is the main positive feed. Another wire will be Purple which is "ignition". This feeds the gauges and keeps the engine running. The third lead is Yellow/Red and it is what activates the starter slave solenoid to crank the engine.

SAFETY TIP:Make sure the shifter is in nuetral and the propellar is removed from the drive. Also make sure that everyone is clear of the engines moving parts.

If you use a little jumper wire and jump across the large Red wire and the Yellow/Red wire the engine should crank. It won't actually start unless the key is on or if you have also jumped the Red to the Purple lead. If the engine cranks when you jump the Red to Yellow/Red lead; but it does not crank when you use the Key Switch, it means you have a bad Key Switch.

If your gauges activate but the engine makes no clicking or cranking noise when you turn the key to the START position, you might have a bad In-Gear-Starter-Protection-Switch. This switch is locted in the remote control. If the shifter is not in nuetral or if the switch is bad, the engine might not crank. Try wiggling the remote control handle in and out of gear a few times and it might work.

Another common item that can prevent the engine from starting is the Safety Lanyard Switch or "kill" switch. Make sure the clip is snapped into place and try to crank the engine again.

SAFETY TIP: Batteries explode. Make sure you have the area around the battery well ventilated. Always disconnect the battery ground before the battery positive. When hooking the battery back up, always connect the positive first and then the negative ground lead second.

Check the obvious. Make sure your battery cable connections are clean and tight. Corrosion can be hidden between the terminal lug and the battery so it is a good idea to remove the lugs and wire brush them off. Check the terminals on the back of the battery switch too. The switch is often a neglected item because it is fastened with screws or bolts and difficult to remove and inspect. Don't rule out the possibility that you have a bad Battery Switch. Also make sure the connections to the motor and Starter Motor are clean and tight.

If all of the above looks good, you might have a bad Starter Slave Solenoid or even a bad Starter Motor.

The Slave Solenoid is a small bracket mounted solenoid usually located near the Breaker or Main Harness Plug. This is the solenoid that everybody knows to jump if the starter won't crank the engine. Careful! It will spark like crazy if you jump the two large terminals. We usually try jumping a positive jumper wire from the positive battery terminal over to the SMALL solenoid terminal that has the small yellow/red wire attached to it. This is the "primary" side of the solenoid which should activate the solenoid and connect the two larger terminals together to supply voltage to the starter. If you jump the solenoid and the engine still does not crank you can jump the larger two terminals. Careful! Jumping the larger terminals will cause sparks. You NEED to use a thick (8 gauge) jumper wire. If you jump the two larger terminals and it cranks OK it means your starter is OK and your slave solenoid is bad. If you jump the two large terminals and it only sparks or nothing happens, you might have a bad starter motor.

If you can crank the engine but it won't start, go HERE.

Boats can explode. Moving parts can rip off your fingers. Hot exhaust can burn you to the bone and props can slice you up. One spark near a battery can cause an explosion. You can never be too careful. Remove the battery from the boat before working with fuel. Always disconnect the batteries negative terminal first. Clean up any spilt fuel and let ALL of the fumes dissipate before installing the battery and starting the motor. Pulleys and Belts can grab your clothes and hair. Don't wear loose clothing and keep your hair up under a hat. Always wear safety glasses. Be smart.
Change your Alpha Gear Lube
Change your Bravo Gear Lube
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Why does my drive lube have gray mush?
Replace Your Alpha One Water Pump
Replace your Alpha Gen II Water Pump
Rebuild your Bravo Raw Water Pump

Troubleshoot & Replace your Alpha Shift Cable
Troubleshoot & Replace your Bravo Shift Cable

Replace your Alpha One Bellows & Gimbal Bearing
Replace your Alpha Gen II Bellows & Gimbal bearing
Replace your Bravo Bellows & Gimbal Bearing
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Replacing your Trim Sender Switches
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Rebuild your Alpha One Upper Driveshaft Housing Assembly
Rebuild your Alpha One Lower Gear Housing Assembly

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Check for Excessive Steering Play
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Troubleshoot a No-Crank Condition
Troubleshoot a No-Start Condition
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I have a Mercruiser 470, 485, 488, 190, 3.7L Engine
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