If your personal watercraft sits in storage for months at a time, you should look into using fogging oil to protect your jet ski engine. STA-BIL Engine Fogging Oil offers a way to keep inactive engine components from becoming corroded over time. 

HOW STA-BIL FOGGING OIL WORKS
When you store any type of vehicle, the lubricants that are in the engine slowly drain away. This leaves engine components dry, and they begin to corrode. When you start the engine for the first time in months, the dry cylinders, valves, and pistons get scuffed up and worn out quickly since they don’t have any lubrication between them. When you apply fogging oil to all these engine parts, you’re essentially coating them in a layer of oil and almost any type of engine, except diesel engines can benefit from this kind of protection!