How to Winterize Boat Fuel

How do you ensure your fuel won’t go bad over the winter and cause problems next season? One school of thought says you must drain the tank, while another claims you need to fill the tank for winter storage. The theory of a full tank is that there won’t be leftover space in the reservoir for condensation to form over the winter. But there are those who would rather a small amount of water in the tank than deal with a full tank of expired fuel.

Today’s Challenges

Today’s E10 fuel presents a challenge. It is mixed with 10 percent ethanol, and therein lies the problem. Ethanol is hydrophilic — meaning that it has the tendency to mix with, dissolve in, or absorb water. During this phenomenon ethanol combines with water and separates from gasoline, descending into a glutenous mass at the bottom of the tank.

Water can get into your boat’s tank though gasket leaks, but since all tanks have ventilation condensation will build up due to fluctuating temperatures. Ethanol can absorb only so much water. Once it becomes completely saturated, phase separation occurs; a condition that cannot be reversed. If you try to run your engine, you will experience significant issues. You want to address your fuel before phase separation occurs or your only option will be a fuel pump off.

Tips for Boat Winterization

Check Hoses

Inspect all hoses for signs of cracks or deterioration. Replace any damaged hoses. Consider replacing the hose clamps and opt for double-clamping each fitting. Make sure to check the lines under the outboard cowl(s), too.

Add Fuel Stabilizer in Advance

Add stabilizing treatments in advance. Doing so allows the additive to circulate through the system before you store the boat for the season.

Fog the Engine(s)

With the boat hauled, fill a remote fuel tank with gas, two-stroke oil, and fuel stabilizer. Connect the tank. Then using a motor flusher over the water pickups, run the engine for five minutes at about 1,000 rpm. Shut it down, and then replace the engine oil and oil filter and lower-unit gear lube.

Change Fuel Filters

Once you fog the engine(s), reconnect the main fuel line and change out the canister on the racor filter (spin-on-type fuel filters). Also, consider changing the secondary fuel filters under the engine cowls.

Changing the Rules

Today’s ethanol-infused gasoline has affected the rules for how to winterize boat fuel. When preparing your boat for winter storage, boat owners must do all they can to avoid phase separation. While this can occur at any time, it is more likely to happen when gas is stored for long periods during fluctuating cold temperatures.

If you have questions or concerns about how to winterize boat fuel in preparation for winter storage, contact Clean Fuels. Our team of experts can help you get your boat ready for the long winter ahead. In addition, once spring arrives, we can test your fuel. Should we discover that fuel phase separation occurred we can provide pump off services.