Water in a Boat Fuel Tank: Symptoms, Causes, and How to Fix It  TLDR Water in a boat fuel tank is one of the most common reasons a gas or diesel engine stumbles, loses power, or quits offshore. Free water is heavier than gasoline and diesel. It...

How a Boat Fuel Tank Vent Dryer Works (and Why Filling the Tank Is Not the Fix) TLDR A marine fuel tank has to breathe. Warm days push air out the vent. Cool nights pull humid marine air back in. Ethanol-blend gasoline and diesel will take up that...

How to Winterize a Boat Fuel Tank Without Phase Separation TLDR A winterized boat with E10 gasoline in the tank is a sitting target for water. Ethanol holds water until a temperature drop or extra moisture pushes it past the saturation point. Then...

Quick summary Diesel bug needs free water. That water often arrives as humid marine air through the fuel tank vent: daytime heat pushes air out, night cooling pulls moist air back in. Ethanol-blend gasoline can also pull water until it...