How to Drain Gas from Boat Fuel Tank? Complete Guide

As the boating season winds down and you enjoy your final day on the water, it’s time to start thinking about storing the boat for the winter. If you usually pull your boat from the water between trips to the lake, or you’re thinking about placing it in storage over the entire winter season, you need to drain the fuel tank first.

Storing your boat with fuel in the lines, engine, and tank will cause untold drama for you the following spring. The fuel separates and clogs everything, causing the need for the mechanic to strip and clean the motor. That will cost you more maintenance fees for the season, and it’s no way to start your opening day on the lake.

Plus, many boatyards and storage facilities require you to drain the fuel tank before storing the vessel to prevent fire risk to the business. Draining the fuel tank should be a best practice you enforce every time you finish using your boat for more than a day between trips.

Draining the tank lowers your maintenance requirements for the season, and it saves you on wear and tear of the motor and fuel system. This brief guide gives you everything you need to drain the fuel successfully.

Equipment for Draining Your Boat Fuel Tank

You’ll need a few pieces of affordable, basic equipment for draining your tank. Typically, you can find everything you need for well under $100. It’s important to choose the right equipment for the job, especially when working with hazardous materials like gasoline or diesel.

You can pick up most of what you need online or at the local marina store.

• PPE – Gloves, Respirator, and Eyewear.
• Fuel Drain Hose.
• Primer Bulb or Transfer Pump.
• Hose Clamps.
• Reserve Receptacle.
• Screwdriver.

It’s important to note that you’ll need to prepare all these materials the day or night before going out on your boat trip.

The last thing you need is to arrive at the staging area to find you forgot your pump. Gather everything for your trip in advance and stash it in the back of your truck or a storage compartment on the trailer.

A Step-by-Step Guide to How to Drain Gas from Boat Fuel Tank

Step 1 – Exhaust the engine.

To drain the fuel system, shut the fuel line to the motor and run it dry. You can do this in the water while waiting for the ramp or outside in the staging area using water muffs. This process removes all the fuel from the carburetor and jets, preventing it from gluing up the fuel system in storage.

Step 2 – Remove the boat from the water and find a level area.

Remove the boat from the water, trailer it and drive it to the staging area. Look for a part of the staging area specifically designated for de-fueling your boat. You should notice drums available for draining your tank. Either that or move to a space away from others in the staging area to complete the transfer. Look for somewhere that’s flat and level.

Step 3 – Don’t forget the safety gear.

Before you start assembling the transfer equipment or start the process of draining the tank, take a minute to think about your safety. You don’t need gas getting on your skin. It absorbs into your blood, where the carcinogens in the gasoline get into your bloodstream.

Breathing in fumes makes you lightheaded and kills brain cells, and there’s always the explosion or fire threat at hand. Keep yourself protected from the worst-case scenario by using the proper PPE for the transfer.

Step 4 – Connect the fuel primer bulb and transfer pump.

Disconnect the fuel hose at the primer bulb, placing it on the inlet barb. Secure the hose with a clamp. We recommend attaching a ten-foot section of line to the outflow barb using a hose clamp.

Step 5 – Connect the drain hose to the fuel tank and receptacle.

Remove the cover of the fuel tank and connect the hose to the opening. Connect the other end to the receptacle and secure the hose in place using hose clamps. Ensure the clamps are on tight so there are no leaks during transfer.

Some boat owners will connect an old gas container designated by the marina for fuel disposal. Others keep the fuel for themselves, and others pump it out into their trucks.

Step 6 – Drain the tank into the reserve receptacle.

Switch on the fuel transfer pump and prime it with the priming bulb. The average transfer pump operates at flow rates of around 33-gallons per hour.

So, you can expect it to drain half a tank from the average bowrider in around 30-minutes to an hour, depending on the model.

Don’t leave the site while the transfer is ongoing. The last thing you need is to get back to the boat to find everything ablaze.

The glass bowl on the pump contains a screen to filter the gas, and when it runs dry, you know the tank is dry. Disconnect the battery and reconnect the fuel line to the motor before stowing the pump and battery for the winter.

Step 7 – Close the tank and seal the receptacle.

After draining the tank dry:

1. Disconnect the drain/transfer hose from the tank and the receptacle.
2. Seal the receptacle first to prevent VOCs from spreading.
3. Prepare the gas for storage, or drive away if you drain the tank into your truck.

How to Drain Gas from Boat Fuel Tank – Key Takeaways

• Always ensure you handle gasoline and diesel as explosives.
• Wear safety gear like gloves, glasses, and respirators where necessary.
• Never drain the tank near anything flammable.
• Keep all flammable materials and flame sources away during the process of draining the tank.
• Secure all hoses and check them before starting the pump.
• Tilt the tank to ensure you dri8an it completely.
• Store unused fuel in a receptacle. Add additives for longer-term fuel viability.
• Keep a fire extinguisher on hand in case of a fire breaking out.

Boat Fuel Tank FAQs

Q: Can I store my unused fuel, and for how long?

A: You can store unused diesel and gasoline for short periods before it starts to separate. Some boaters use additives to prevent the fuel from separating, but even these additives have a lifespan, and the fuel eventually goes bad.

Q: Where is the best place to store my unused fuel?

A: Some people store the fuel in a receptacle like a steel oil drum. Others decant the fuel straight into their truck gas tank; it depends on your setup.

Q: Do storage yards allow me to store my boat over winter with fuel in it?

A: Most yards will demand that you remove all fuel from the tank before storing your boat in dry storage facilities.

Think about it, if everyone left their fuel in the boat, that would present one huge fire hazard for the storage facility. Therefore, you’ll have to drain the tanks before storing the boat for the winter.

Q: What happens to my boat motor if I use bad fuel?

A: Bad fuel separates over six to ten weeks, depending on the manufacturer. Some blends may even start separating after as little as a few days in the tank, especially under heat stress.

Running separated or “bad” fuel through the motor blocks the jets and damages the internal components while clogging up the fuel filter.

In short, you’ll end up spending hundreds in maintenance when they have to open the motor to clean it out.

Q: Should I store my fuel or dispose of it at the marina/shipyard?

A: It depends on how long you intend to be out of the water. If you’re using the boat on weekends and you have a significant amount of fuel, you might get away with using it the following weekend without worrying about problems with separation.

If you’re storing it for the winter, then the chances are the fuel will be bad by the time you want to use it in the spring or summer. So, it’s better to dispose of it in the yard after draining the tank in this scenario.

The Final Thought – Be Careful when Draining Gas and Treat It as an Explosive

Look around the marina and the staging area next time you’re at the launch, and you’ll find it amazing how people handle gasoline. Some people treat it as if it were no more harmless than seawater. You can see this behavior in some people at the pump when filling up.

Don’t ever be blasé with handling gasoline; treat it with respect at all times. Gas explosions and fires happen all the time, and most of them occur due to handling errors by people that don’t have any thought about safety.

As long as you treat gasoline as you would any other dangerous material, you’ll be fine. Follow the tips in this guide, and you’ll have a dry tank and your boat ready for storage in no time.