Every boat owner will go through the task of cleaning the boat fuel tank at some time.
But how do you clean the tank properly without causing damage or contamination?
These marine fuel tank cleaning instructions apply to boat owners of inboard and outboard engines like sailboats, motorboats, catamarans, yachts, pontoons, speedboats, deck boats and trawlers.
To clean a boat fuel tank, follow the steps:
- Drain The Fuel Tank
- Disconnect The Fuel Lines From The Fuel Tank & Clean Them
- Pour Fuel Tank Cleaner Into The Boat's Fuel Tank & Pressure Wash It
- Remove The Boat's Fuel Filter & Clean Or Replace It
- Reattach The Fuel Lines & Fill The Tank With Clean Fuels
- Start Up The Engine & Leave It In Idle For 10 minutes
This guide highlights how to clean contaminated marine fuel tanks, remove sludge, unclog fuel lines and rejuvenate old gasoline and diesel fuel.
It will help you to clean a boat's gas tank that has been sitting for some time.
Some boats will have specific instructions when cleaning the fuel tank. In this scenario, check the boat owner's manual for instructions specific to your boat.
The goal is to have a sparkling clean tank and remove any fuel-tank contamination and rust.
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Step 1: Drain The Boat's Fuel Tank
The first step for cleaning a boat fuel tank is to drain the fuel from the vessel's fuel tank.
To drain a boat fuel tank:
- Get a fuel suction pump: Use a fuel suction pump and connect the syphon hose to the fuel in the fuel tank and a bucket
- Manually pump the fuel out and remove the fuel from the boat's fuel tank: Use the fuel suction pump to manually pump the fuel out from the boat's fuel tank into a bucket. For larger boats with very large fuel tanks, use a motorized suction pump to speed up the process
- Continue pumping until the boat fuel tank is empty: Continue the process of pumping the boat fuel out of the fuel tank until it is completely empty and dry
- Use a sealable bucket to hold the fuel: Use a sealable bucket when draining the fuel tank to ensure there are no spillages or foul odors
For the majority of vessels, draining the fuel tank with a suction pump should take between 10 and 20 minutes to complete.
For larger boats with larger fuel tanks, draining the fuel tanks should take between 30 minutes to over 1 hour to complete.
Using a fuel suction pump also helps with cleaning the boat's fuel tank without removing it.
The how to remove bad fuel from a boat fuel tank guide will also help with safely removing dirty and contaminated fuel.
Summary
Draining the boat's fuel tank can be done by using a simple fuel suction pump and connecting a syphon hose to the fuel and a bucket.
Step 2: Disconnect The Fuel Lines From The Fuel Pump & Clean Them
The second step when cleaning a boat's fuel tank is to disconnect the fuel lines from the fuel pump, fuel tank and boat engine.
To disconnect the fuel lines from the boat's fuel tank & clean them:
- Remove the screws that hold and connect the fuel lines to the fuel tank: Use a screwdriver or spanner to loosen and remove the screws that help connect the fuel lines to the fuel tank (where applicable)
- Pull the fuel lines off slowly: Once the screws have been removed, slowly pull the fuel lines off the fuel pump and fuel tank. Remove them slowly to ensure you don't damage them
- Use a marine cleaner to unclog or remove dirt from the boat's fuel lines: Use a marine-grade fuel cleaner to unclog or remove any dirty fuel lines. You can also manually use a thin brush and push it through the fuel lines to ensure there is no dirt
The majority of boat fuel lines can be removed and cleaned by following these steps.
However, some less common boat motors require different instructions. In this scenario, use the boat engine manual as a guide.
Disconnecting the fuel lines when cleaning a boat's fuel tank is useful because it:
- Helps find and remove trapped dirt in the fuel lines: Sometimes there is a buildup of dirt in the actual fuel lines. Disconnecting the fuel lines makes it easy to unclog them from sludge and easily clean the fuel lines themselves
- Stops cleaning water getting trapped in the fuel lines: Isolating and disconnecting the fuel lines will help stop the water you use to clean the tank from getting trapped in the fuel lines which could be a problem when you reattach them and attempt to start the engine
- Makes it easier to clean both the boat's fuel tank and the fuel lines: Having the fuel lines disconnect helps make it easier to clean the fuel tank itself and it also helps to identify dirt in the fuel lines and remove it
Disconnecting the fuel lines from the fuel pump and cleaning them should take approximately 10 to 15 minutes to complete.
Summary
Disconnecting the fuel lines will help stop cleaning water from getting trapped in the fuel lines. It will also help spot clogged or dirty fuel lines.
Step 3: Pour Fuel Tank Cleaner Into The Boat's Fuel Tank & Pressure Wash It
The third step of cleaning a boat's fuel tank is to pour a fuel tank cleaner into the empty fuel tank, pressure wash it and then drain it again.
After pouring fuel tank cleaner into the boat's fuel tank:
- Use a brush to scrub the fuel tank walls: Use a brush that fits into the fuel tank and scrub the fuel tanks walls to get the hardest dirt and sludge off it
- Place the nozzle of the power washer inside the fuel tank and pressure wash it with warm water: Use the pressure washer to blast the dirt and sludge that is trapped inside the fuel tank
- Drain the soapy water from the fuel tank: After pressure washing the fuel tank, drain it again to remove all the soapy and dirty water. It is very important that it is completely drained with no water or dirt left in the tank. Use a sealable bucket or container when draining the fuel tank again
A marine-grade fuel tank cleaner will help to remove the sludge, varnish and dirt trapped in the fuel tank and ensure the new clean fuel put into the fuel tank won't go bad or get contaminated.
It's important to only choose a marine-grade fuel tank cleaner that is compatible with your specific boat's fuel tank. i.e. a gasoline fuel tank cleaner or diesel fuel tank cleaner.
For the majority of recreational boats, pouring fuel tank cleaner into the boat's fuel tank, scrubbing it with a brush, pressure washing it and draining out the dirty water should take approximately 30 minutes to 45 minutes to complete.
For larger boats with much larger fuel tanks, it can take over 90 minutes to complete.
Summary
Fill the fuel tank with fuel tank cleaner, scrub it with a narrow scrubbing brush, power wash it with a pressure washer and drain out the dirty water.
Step 4: Remove The Boat's Fuel Filter & Clean Or Replace It
The fourth step of cleaning a boat's fuel tank is to remove the vessel's fuel filter and clean or replace it.
To remove and clean the boat's fuel filter:
- Use a spanner or screwdriver to detach the fuel filter from the fuel pump system: Use a spanner or screwdriver to loosen the screws that keep the fuel filter attached.
- Clean the dirty fuel filter or replace it with a new one: Once the fuel filter has been detached, clean it with a cloth or sponge by wiping away dirt and dust or replace it with a new one. A fuel filter can be purchased for under $50 depending on the type of boat
- Reattach the fuel filter and connect it to the fuel pump system: Use a screwdriver or spanner to reconnect the fuel filter to the fuel pump system
Cleaning or replacing a boat fuel filter with a new one ensures there will be no impurities flowing into the engine or the fuel tank.
If you're unsure where your specific boat's fuel filter is located, read your boat's engine manual for instructions specific to your type of boat.
Removing & cleaning or replacing a boat's fuel filter should take approximately 20 minutes to complete at most.
Summary
Remove the boat's fuel filter and either clean it or replace it with a new one. This is a quick way to ensure no impurities flow into the fuel tank.
Step 5: Reattach The Fuel Lines & Fill The Tank With Clean Fuel
The fifth step of cleaning a boat's fuel tank is to reattach the fuel lines and fill the vessel's fuel tank with clean fuel.
To reattach the fuel lines:
- Reconnect the fuel lines to the fuel system: Reconnect the fuel lines that attach the engine and fuel tank system together
- Use a screwdriver or spanner to tighten the fuel lines: Use a screwdriver or spanner to tighten the fuel line attachment and ensure there are no leaks
Once the fuel lines are reattached properly and the fuel tank is completely dry with no residual water or dirt, fill the tank with fresh, clean fuel.
If you're unsure about reattaching the fuel lines on your specific boat, use the boat's engine manual as a guide.
Reattaching the boat's fuel lines and pouring new clean fuel into the fuel tank should take approximately 15 minutes for most recreational vessels.
For larger boats with much large fuel tanks, this process can take over 1 hour to complete.
Summary
Reattach the boat's fuel lines and fill the fuel tank with new fuel.
Step 6: Start Up The Motor & Leave Idle
The sixth step of cleaning a boat's fuel tank is to start up the engine and let it sit idle for 10 minutes.
While the boat motor sits idle for 10 minutes:
- Check for any warning lights in the cockpit: Once the engine is started, it's important to let the engine sit idle and watch the cockpit area for any warning lights that may show up. If there is an issue, it's better to solve it before going out on the water
- Ensure there are no issues around the fuel tank area: Letting the boat sit idle for 10 minutes also means you can check around the fuel system area for potential leaks or issues around the fuel lines areas that you may have missed when reattaching them
If everything is running smoothly and there are no warning lights or visible issues around the boat engine, you should be finished cleaning the boat's fuel tank and ready to go.
Summary
Start up the engine and let it run for 10 minutes to make sure everything is running properly after the fuel tank is cleaned.
Boat Fuel Tank Cleaning Products To Use
When cleaning a boat fuel tank, the products needed are:
- Fuel suction pump: This is needed to drain the fuel tank before cleaning it. You can get either a manual fuel suction pump or a motorized one more suitable for larger boats
- Sealable bucket or container: This is needed to store the bad fuel and dirty and soapy water from cleaning the fuel tank and ensuring the cleaning is done in an environmentally friendly way
- Fuel tank cleaner: This is needed to help remove the dirt and sludge from the inner walls of the fuel tank. Ensure you only get a cleaner compatible with your specific fuel
- Power washer: This is needed to help blast away the dirt and sludge inside the boat's fuel tank
- Fuel filter (Optional): If the boat needs a new fuel filter, you'll need to get one that is compatible with your boat's fuel system
- Gloves: A pair of gloves are needed to protect your hands from toxic materials while cleaning
- Narrow scrubbing brush: This is needed to help scrub the inside of the boat's fuel tank and assist you in cleaning those hard-to-reach areas inside the fuel tank
These items should be sufficient for cleaning a boat fuel tank.
We also recommend checking the list of the best boat fuel tank cleaning products to help ensure the right items are used to clean the tank. Alternatively our top boat cleaners review may help find the right products for the job.
Ongoing Boat Fuel Tank Cleaning
As part of regular fuel tank maintenance, use a fuel system cleaner to mix with the fuel in the boat engine.
This boat fuel cleaner will help prevent contamination of the fuel and ensure the boat's fuel tank is kept clean on an ongoing basis.
It will also protect against a build of dirt and sludge in the future.
Regularly cleaning the fuel tank is great for keeping the fuel flow running efficiently.
Alternative Fuel Tank Cleaning Options
When looking to clean a boat's fuel tank, alternative cleaning options available are:
- Hire a fuel tank cleaning company: A boat cleaning company will come and clean the tank for you. The cost of cleaning a boat fuel tank ranges from $45 to over $300 for larger boats when using a professional cleaning service
- Hire a professional individual to clean the fuel tank: Find a professional on Craigslist or a local classified site to wash and clean out the fuel tank
These options are best for those that want to outsource the cleaning work.
Boat Fuel Tank Cleaning Benefits
The boat fuel tank cleaning benefits are below.
- Removes Dirt and Sludge: Cleaning the tank will remove the sludge-type material from causing damage to the engine and tank
- Prevents Fuel Contamination: Fuel contamination can cause serious engine damage. Marine fuel can get contaminated when water, sludge or dirt mixes with boat gasoline or diesel. With regular maintenance, water will not mix with fuel and cause damage
- Prevents Boat Engine Damage: Cleaner fuel tanks mean better overall engine performance and regular marine fuel tank cleaning maintenance will help prevent boat engine damage
- Prevents Boat Fuel Tank Rusting: Cleaning the tank regularly means rusting can be treated sooner
- Improves Fuel Efficiency: No dirt in the fuel tank means better fuel flow through the engine which helps overall engine health
- Reduces Fuel Emissions: Cleaning the fuel can help emissions and protect the environment
- Helps Spot Fuel Tank Damage: Cleaning the fuel tank regularly enables you to spot cracks before it becomes a major issue
Frequently Asked Questions
Below are frequently asked questions about boat fuel tank cleaning.
How Often Should You Clean A Boat Fuel Tank?
A boat fuel tank should be cleaned once every 3 months on average.
How Long Does It Take To Clean A Boat Fuel Tank?
A boat fuel tank takes between 30 minutes and 6 hours to clean depending on its size and condition.
What Is The Boat Fuel Tank Cleaning Cost?
Boat fuel tank cleaning costs between $45 and $300 depending on size and condition of the tank.