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Lesson 3 - Engine Checks

Overview

In this lesson, we focus on one of the most critical aspects of yacht care—engine maintenance and troubleshooting. Your yacht engine is essential for maneuvering in marinas, maintaining control when the wind dies, and ensuring a safe and smooth journey. A breakdown can quickly turn a great trip into a stressful situation.

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By the end of this lesson, you will understand:

  • How to perform daily engine checks to prevent issues

  • How to troubleshoot common engine problems

  • What different engine symptoms mean and how to respond

  • When to seek professional help

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The WOBBLE Check

Before taking apart the engine, start with these five essential checks:

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  • Water – Ensure seawater is flowing through the cooling system and that coolant levels are topped up.

  • Oil – Check engine and gearbox oil. Milky or thick oil indicates contamination or an issue.

  • Belts – A loose or broken alternator belt can cause power loss and cooling system failure.

  • Batteries – Ensure they are charged above 12.5V and check for loose or corroded terminals.

  • Leaks – Look for any signs of water, oil, or fuel leaks in the bilge or around the engine.

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Small issues caught early can be fixed before they escalate into major problems.

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Step 1: The Engine Won’t Start – Where to Begin?

If you turn the key and nothing happens, work through these checks:

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  • Kill Switch Engaged? Many engines have a safety kill switch that must be disengaged before starting.

  • Gear Lever in Neutral? Some engines will not start unless the throttle is in neutral.

  • Battery Power Check

    • If you hear a clicking noise, the battery may be low.

    • Use a multimeter—12.5V+ is good; below 12V means the battery needs charging.

    • Try switching to another battery bank if available.

  • Fuel Supply Issues

    • Ensure there is enough fuel in the tank.

    • Check the fuel shutoff valve—if it is closed, fuel is not reaching the engine.

    • If the engine ran out of fuel recently, there may be air in the fuel lines, requiring bleeding.

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If these steps do not resolve the issue, move to the next troubleshooting stage.

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Step 2: The Engine Starts… But Then Dies

If the engine runs for a few seconds and then stops, consider the following causes:

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  • Blocked Fuel Filter – A clogged filter can starve the engine of fuel.

    • Replace the fuel filter and check for water or dirt in the fuel bowl.

  • Overheating Shutdown

    • If an alarm sounds before the engine cuts out, the cooling system may be compromised.

    • Check the raw water intake strainer for blockages like seaweed or debris.

    • Inspect the impeller—if damaged, it will fail to pump water properly.

  • Exhaust Blockage – A blocked exhaust can prevent the engine from running.

    • Check for kinks in the exhaust hose or carbon buildup.

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Step 3: The Engine Runs Rough – Shaking, Stalling, or No Power

If the engine is running but seems unstable, these could be the causes:

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  • Dirty Fuel Injectors – Diesel fuel additives can help clean deposits.

  • Loose Engine Mounts – Excessive vibration may indicate loose bolts that need tightening.

  • Misfiring Cylinders – Hard starts or rough idling could point to faulty glow plugs or fuel injector issues.

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A rough-running engine is a sign of an underlying problem—address it early to prevent further damage.

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Step 4: The Engine is Overheating – How to Fix It?

Overheating is a major cause of engine failure and can lead to serious damage.

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  • Raw Water Intake Blocked?

    • Check the sea strainer for debris like seaweed or plastic.

  • Broken Impeller?

    • If the impeller is not functioning, it will fail to circulate cooling water.

  • Low Coolant?

    • Check the coolant expansion tank and top it up if necessary.

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Important: Never open a hot coolant cap—it can cause severe burns. If the engine continues overheating, shut it down immediately to prevent further damage.

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Step 5: What’s That Smoke? Understanding Exhaust Fumes

Different exhaust smoke colors can indicate specific engine problems:

  • White Smoke – Possible water contamination in the engine.

  • Grey or Blue Smoke – Oil is burning, which could indicate an oil leak in the combustion system.

  • Black Smoke – Unburnt fuel, often caused by a blocked air intake or injector issue.

Observing exhaust fumes can help diagnose engine problems before they become serious.

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Step 6: When to Call for Help

If none of these troubleshooting steps resolve the issue:

  • Do not force the engine – Attempting to start a damaged engine can worsen the problem.

  • If near shore, contact a marine mechanic for assistance.

  • If at sea, contact your charter company for guidance. If the situation is critical, use VHF to request emergency assistance.

Knowing when to stop troubleshooting and call for help can prevent further damage and ensure safety.

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Key Takeaways

  • Perform daily engine checks to catch issues before they escalate.

  • Use the WOBBLE method to systematically inspect the engine.

  • If the engine won’t start, check the kill switch, battery, fuel, and gear position.

  • A rough-running engine may indicate dirty fuel injectors, loose mounts, or misfiring cylinders.

  • Overheating is a major issue—check the raw water intake, impeller, and coolant levels.

  • Pay attention to exhaust fumes—they often signal internal engine problems.

  • Know when to call for help—some problems require professional assistance.

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