How Your Drain Old Gas From Your Boat's Fuel Tank

Draining old gas from your fuel tank is an important step in boat maintenance, as it helps prolong the life of your tank and keeps the engine running smoothly. When it does come time to take your boat out of the water for the season, draining the fuel tank can prevent residue build-up in the off-season. But how exactly do you empty your boat’s fuel tank, and is it something you can do yourself?

Every boat enthusiast knows that boating and fishing can be an expensive hobby, so learning to drain your fuel tank will help you save some expenses. Here, we'll cover the tools you need to successfully drain your fuel tank and the steps necessary to do it on your own. 

The Tools You’ll Need

Siphoning old gas out of a boat fuel tank can be done relatively cheaply, depending on the type of fuel pump you use:

• Manual Fuel Pump. There are different types of manual pumps, which are typically sold as kits at your local marina store. As the name implies, you have to run the pump manually to drain old gas from your boat’s tank. This is a good choice for those who only need to drain their boat's fuel pump occasionally (once a year, before the off-season, ideally). Most kits also come with a 3/8-inch fuel hose. If the kit you buy doesn't come with a hose, you'll need to purchase one separately.
• Electric or Battery Pump. An electric pump is much easier and more efficient at draining a fuel tank, but these are a bit pricier. Good electric and battery-operated pumps can range anywhere between $150 and $300. For an electric model, you do need an extension cord to drain the tank.

You will also need somewhere to securely store the old fuel as it's draining. Make sure you have an appropriate fuel container or gas can handy, which is large enough to capture all of the fuel as it's being siphoned from the tank.

Finally, it's a good idea to wear basic safety gear when handling boat fuel. Depending on your comfort level, you'll likely need a pair of rubber gloves. Fuel is a skin irritant, so you'll want to avoid letting it come in contact with your skin. A pair of goggles is also a good idea. If the smell of fumes from gas bothers you, a face mask can help, as well.

How to Drain Gas from the Fuel Tank: Step By Step

Step 1: Run the Boat if Necessary

Depending on how much gas is still in the tank, you may want to run your boat to reduce the fuel level further. Less than 1/8 of a tank is a good range to have on the boat's fuel gauge before draining it. If necessary, go for a quick ride before draining your tank.

Step 2: Remove Your Boat from the Water

Whether you have a lift on your private dock or boathouse, or you opt to lift your vessel onto a trailer, you will need to remove it from the water to properly drain the fuel tank.

Step 3: Put on Protective Gear

Make sure you’re wearing your safety gear and that your boat is in a dry, well-ventilated place.

Step 4: Position Your Fuel Container

Whatever type of receptacle you opt to use to store the old gas, it needs to be lower than the boat's fuel tank for the transfer process to work. It will also need to be within range of the hose.

Step 5a: How to Use a Manual Pump

If you're using a manual pump, submerge the suction pump in the gas tank. The pump should be attached to the hose, so just make sure you have enough slack to reach the bottom of the tank. Put the other end of the hose in the container you're using to catch the fuel. Start operating the manual pump until fuel starts freely flowing through the hose. The tank should fully drain within a few minutes, depending on how much fuel is in it.

Step 5b: How to Use an Electric or Battery Pump

An electric pump will also have a suction pump attached to a hose at one end. Submerge the suction pump into the tank and put the other end of the hose in your container. Flip the switch on the pump and allow it to completely drain your tank. If the steps are slightly different in the owner's manual for the electric or battery pump you've chosen, follow those steps exactly.

Final Steps for Emptying a Boat Fuel Tank

Be sure to dispose of the old gas properly. Take it to your local hazardous waste disposal center. It's also important to clean the hoses on your fuel pump. Fuel residue can still ignite under the right conditions, so flushing the hoses and pump will prevent this.

That's all there is to it! Your boat's fuel tank is now empty and ready for the off-season. This is a relatively simple maintenance task that will provide added longevity for your boat’s fuel tank and engine. 

At Gemlux, we’re here to provide you with pro tips for keeping your vessel in ship-shape year round. To learn more about how to install and store boating and fishing equipment, as well as care for and properly maintain your vessel, check out our videos!