Water trapped inside a lawnmower will bring it to an immediate standstill. Water logging typically occurs when lawnmowers sit outside, where they are exposed to rain, or when you do not screw caps back on. Moisture usually gets trapped in the gas tank and, from there, enters the carburetor bowl. Sometimes water can also seep into the oil supply, which will result in milky white oil. Fully drain any reservoir potentially compromised by moisture to return a lawnmower to working condition.
Disconnect the spark plug for safety.
Siphon the diluted gas. Insert the siphon tube of a hand-pump into the gas tank of the lawnmower. Insert the drain tube in a gas disposal container. Pump the siphoning device to begin transferring the liquid from the gas tank.
Drain the oil. Prop up the front of the mower on blocks. Place an oil pan under the machine's drain plug, located on the underside of the mower. Unscrew the drain plug with a wrench and allow the oil to drain into the pan. If no drain plug exists, lift the mower from the side where the carburetor or air filter is located and pour the oil from the oil fill hole.
Empty the carburetor bowl, a metal cylinder located on the side of the machine. Wipe around the bowl with a rag dampened with carburetor cleaner to prevent dirt from falling in once removed. Place a rag under the bowl to catch liquid. There will be at least one set bolt. If there is a second, offset bolt, it is a drain plug. If no drain plug exists, unscrew the bolt to remove and pour out the contents of the carburetor bowl.
Wipe out the insides of the gas tank, oil tank and carburetor bowls with clean rags. Dispose of old oil and water at a local hazardous waste recycling facility.