Drain the engine, clean the personal, fill it with gas, fog and lubricate and remove the battery to winterize a personal water craft. Some steps may vary and additional procedures may be necessary depending on the make and model of the unit being winterized, but typically the steps listed are similar for all types of personal watercraft.
Park the trailer with the personal watercraft on an inclined slop and drain all of the water remaining in the engine and intakes. Clean the inside and outside of the hull thoroughly and use a wet-vac to remove any water remaining in the storage compartments. Clean or replace the fuel filter, and fill the gas tank with fresh fuel to prevent condensation buildup inside of the tank. Add the appropriate fuel stabilizer for the type of engine, and start the engine for 15 to 20 seconds to let the stabilized fuel circulate into the engine.
Grease the drive train, remove the air filter, start the engine, and spray fogging oil directly in the throat of the carburetor until the engine dies. Remove the spark plugs, and spray fogging oil into the mounting holes. Place a rag over the holes, and press the start button to disperse the oil.
After the battery is removed, clean the terminals and battery case with a mixture of baking soda and water, and fill the battery's cells with distilled water. Store the battery in a warm space such as a storage shed or garage.