Your best bet for what you are wanting to do is to buy either a Kawasaki or Yamaha 3 seater that is at least a 1200 cc motor. Kawasaki and Yamaha have been around the longest and have the best technology. They are also by far the most reliable and are the easiest to find parts for. Yes Polaris and Sea Doo also make popular jet ski's but they are not as reliable. Same with all of the other brands too.
The things to look for are has the ski been ridden in fresh water or salt water? If any salt water at all, what did they do to maintain it afterwards? A very minimum should be the engine was flushed out while running for at least 15 minutes with hose water and the engine compartment should also have been washed out and rinsed then sprayed with WD-40. How many hours are on it? If your buying used, the lesser the better. Anything over 100 hours, I would stay away from because chances are, at those hours, you are getting close to replaces pricey parts. Yes some will last well into several hundred hours with no problems but for a used ski, there is not a huge savings so find something with low hours for the same amount of money. How has the ski been stored and in what weather? If it has been garaged, that is good but if it has been left outside and exposed to the elements, that will also really effect a ski. What kind of preventative maintenance has been done to it? Has the ski ever sunk or has water ever gotten into the engine? If so, move on to the next ski! Check the impeller for damage along with the drive shaft. It's amazing that every time I go to the lake, there is some idiot buzzing his ski right next to the shore line in less than 3 feet of water. All that idiot is doing is sucking up sand through his impeller and damaging it. Does it start up good even when cold? Also, put it in the water and test it! One these motors have a water load on them, they can run very differently. Even if you only watch the owner ride it, you can at least tell it runs good in the water.
