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Marine Diesel Engines | Cleaning the Raw Water System

Marine diesel engines stand as the powerhouse of choice for seasoned mariners, valued for their efficiency, durability, and reliability. Their ability to efficiently consume fuel not only reduces operating costs but also extends a vessel's range. That being said, maintaining these robust engines is crucial, especially when it comes to their raw water systems. Regular cleaning is essential, particularly for boats in seawater where calcium buildup and biological growth can significantly impact performance and longevity. Today we'll delve into a best practice for cleaning your marine diesel engine raw water system, which was originally shared with us by Chad at Just Catamarans. Our focus will be on diesel engines of 80HP and below with saildrives; however, you can modify this to be accomplished on larger diesel engines and those with drive shafts as well.

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Supplies List

Frequency & Duration

While frequency may vary depending on the salinity of your geography, we find that once every 6 months will do the trick. With 2 people, the process should take about 25 - 30 minutes per diesel engine, and is one of the most simple and inexpensive maintenance tasks you can do to elongate the life of your marine diesel engine.

Overall Purpose

Over time marine diesel engines, especially those in seawater, will build up heavy calcium and biological growth throughout the system. This causes engine performance to suffer, and ultimately resulting in irreversible damage to hoses, fittings, seals, pumps, heat exchangers, and exhaust elbows. Cleaning your system regularly will elongate the life of these components by YEARS, and ensure the performance of your marine diesel engine remains top notch!

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The Process

  1. Remove engine sea strainer cap and pour approximately 1 quart of Barnacle Buster Concentrate into the strainer, or until it fills to the label line.

  2. Close the valve to the saildrive raw water intake

  3. Have one person start the engine while the second person pours the remainder of the gallon of Barnacle Buster into the sea strainer

  4. Kill the engine once all the Barnacle Buster is inside the system/strainer

  5. Place cap back on the sea strainer

  6. Open the saildrive intake valve, then wait 20 minutes

  7. Start the engine and watch the exhaust - calcium deposits, growth, and all sorts of other garbage will likely come out along with discolored water

  8. Run the engine until the exhaust air and water are back to normal, then shut down the engine


Maintaining the raw water system of your marine diesel engine is a critical aspect of boat upkeep, particularly for those being used in seawater. By utilizing Barnacle Buster and following the simple steps outlined above, you can easily clean the system regularly, preventing harmful calcium build-up and biological growth. Investing a little time and effort into cleaning your engine's raw water system can add years to the life of major components and ensure optimal performance, making your boating experience more enjoyable, trouble-free, and less expensive to maintain.

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