Diesel Fuel Polishing for Your Boat

If you have a fuel-efficient boat, you are naturally benefiting from lower fuel costs. You spend less money to reach the same destination. However, a fuel-efficient engine is not necessarily a cleaner engine. Using less fuel may result in fuel that becomes stagnant and highly contaminated. This can create premature wear and tear on the engine, causing you to spend more money on repairs or a complete engine replacement. 

A diesel fuel polishing system ensures that your boat’s engine burns pure fuel, resulting in an overall cleaner burn with fewer problems. While there is nothing new about fuel polishing systems, they were originally relegated to larger crafts. Now owners of smaller yachts and other vessels can use diesel fuel polishing systems to keep the engines operating at peak levels while preserving their fuel efficiency.

What Happens When Diesel Fuel Sits in the Tank?

If you own a diesel-powered yacht, you know the challenges that come with contaminated fuel. Bacteria, algae, mold and yeast can grow inside the fuel tank and contaminate the fuel while clogging the fuel filter. How do these microorganisms invade the fuel? They develop as a result of moisture getting in the fuel tank. 

As the microbes build up, they clog the fuel filter. This creates a domino effect that starves the fuel pump and airlocks the engine. Eventually, the engine stops working because it is not getting enough fuel to power the boat. To prevent the growth of harmful microbes, you need to remove the water in the fuel before the organisms have a chance to take root.

The Solution: A Diesel Fuel Polishing System

To remove the water and microbes from your diesel fuel, you need to use a fuel-polishing system. A polishing system pumps diesel fuel out of the tank. The fuel flows through a fuel-water separator and a filter. From there, the fuel returns to the tank, free of all contaminants. The process of filtering impurities out of the fuel system ensures that the fuel is clean before it runs through the boat engine’s fuel system.

The size of the polisher depends on the boat’s fuel capacity. For instance, a larger yacht’s fuel system is designed for extended cruises. As a result, there is more fuel to purify. Therefore, you would need a higher-capacity polish to ensure that the fuel stays clean while the boat is in operation. Most polishing systems are rated according to their capacity, A.K.A., gallons per hour (GPH). 

What to Consider When Using a Diesel Fuel Polishing System

To get the most out of your fuel polishing system, follow these simple guidelines:

Low Tank Position

Fuel contaminants accumulate at the bottom of the fuel tank. Over time, they buildup and then clog the fuel filter. Therefore, make sure you buy a polishing system that you can install as low to the bottom of the tank as possible. The lower the system, the more microorganisms the polishing system will filter out of the fuel. 


If the diesel fuel in the tank has been sitting for a while, you may want to add a little fuel to the tank before inserting the polishing system. By adding more fuel, you stir up the growth and sediment from the microorganisms settled at the bottom of the fuel tank. The contaminants dispersed throughout the tank are more likely to get pulled into the polishing system filter.

Changing the Filter Element

Polishing system manufacturers make different recommendations on how often you should change your diesel fuel polishing system’s filter element. Some companies recommend changing the filter element out at regular intervals. Other manufacturers recommend changing the element after each use. Still, other companies recommend changing the element based on its condition. Make sure you read the user manual and follow the manufacturer’s specifications regarding changing the fuel polishing system filter element. 

What Are the Benefits of Fuel Polishing Systems?

A fuel polishing system is only necessary if fuel is allowed to stay in your boat for an extended period. Since most boat engine manufacturers recommend that you store your boat engine with the tank almost full, that means there is a high probability that fuel will be allowed to sit in the tank for a longer period sometime throughout the year. Therefore, you probably need a fuel polishing system to purify the fuel once you get the motor up and running again.

Since boat fuel is a significant expense to any boat operation, there are some advantages to using a fuel polishing system.

1. Repurposes Consolidated Fuel

Over time, diesel fuel condenses slightly after it has been in storage. Although a fuel filter removes the condensed solids in the fuel, a fuel polishing system repurposes the solids by extracting them and processing them back into liquid form.

2. Uses Otherwise Bad Fuel

Fuel that is filled with contaminants is technically bad. Even if it is usable, it can harm your boat engine. A fuel polishing system can turn bad fuel into healthy fuel simply by filtering out the harmful microbes. Instead of flushing out the old fuel, you can save money by cleaning it.

3. Extends the Life of a Fuel Filter

On average, boat fuel filters last 100 hours. They only last this long because the fuel is often dirtier than it should be. A fuel polishing system can extend a fuel filter’s life and keep it clean, improving its function.

4. Saves Money in Engine Repair Costs

As microorganisms build up in your fuel tank, they are dispersed throughout your boat engine’s system, causing it to become more contaminated over time. As your engine gets dirtier, it takes more effort for the engine parts to work. Eventually, these parts wear out and need to be repaired or replaced. A fuel polishing system can keep your engine clean and keep you from making costly repairs sooner than necessary. 

Contact Pensacola Shipyard Today

Pensacola Shipyard is the Emerald Coast’s premier boatyard. Whether you need ongoing boat maintenance, resources or facilities, we have everything you need for a complete boating experience.

To find out more about our marina and boating services, call 850.780.8441.