ConclusionRemove the cover and seat, charge and install the battery, check the engine and fluids (oil, coolant, etc.). Make sure that all water has been drained from the engine and from the entire jet ski. When you put your personal watercraft in the trailer, position it so that the stern is lower than the bow. This will help it drain naturally.
If there is water left, you can start the engine for quick intervals of 15 to 20 seconds and accelerate a couple of times. This will force everything left to come out. With the throttle fully depressed, hold down the start button and turn the engine several times. When the throttle is fully engaged, it prevents the engine from starting.
Some Waverunner models require you to hold down the start and stop button simultaneously instead of the throttle. The first thing to do (after removing the cover) is to check the fuel line and cooling lines. You need to make sure that no cracks or leaks form during the winter. A broken fuel line is a quick way to get trapped in water.
While doing so, check all cables and straps to make sure they aren't loose or damaged. If you live in a warm climate, you may be able to simply keep your jet ski on a damp dock and “preparing for winter is more of a form of speech; however, if you live in a state where temperature drops are drastic and include freezing temperatures, your jet ski will require thorough preparation for winter and storage. You can do this on a boat ramp, a jet ski chairlift, or lift the front with materials found around your garage. You shouldn't use a heating lamp to keep your jet ski warm during the winter and instead make proper winterization.
Always store your jet ski with a full tank to prevent condensation from forming on any exposed surface within the fuel system. Gaskets tend to be the most common form of seals for jet ski engines, and making sure you have the right material for your gaskets will help their service life. I use fogging oil to spray the cable to the ski throttle and try to pull it up the cable under the ski seat. Before starting your jet ski for the first time of the season, you'll want to remove your seat and check the fuel and cooling lines for cracks or damage.
Since jet ski dealers are slower during the winter, they often have better winterization rates with the oil change, so now would be the best time to do so. When you take the jet ski out, you'll want to make sure that the pump and impeller inside the pump are in good working order. That said, it's a good idea to give yourself additional time to prepare your jet ski before you plan to take it out. I know this doesn't sound like much fun, but an inspection is precisely what your jet ski will need when removing that dusty cover.
Then place a rag over the holes and start the jet ski so that the oil covers the internals without spraying oil everywhere. Make sure that the back of the jet ski is not in the water and make sure that the jet ski is also secured to the dock. Don't just try to improvise this, as each different jet ski will have its own set of instructions for using the antifreeze.