i just bought a 2006 150 sportster, if you cant water test the boat, a seadoo dealer can hook it up to a computer and read the motor (it's called B.U.D.S) it will read hours on boat from new, how the boat was ran (rpm's), if it ever had any diagnostic issues, and a bunch more info. my boat had 35 hours on it when i bought it, and the boat looked like new, motor was clean as a whistle, so it looked like the previous owner took care of it. pulled oil dipstick and oil was clean (not black) I ran the boat on the lake for the first time and ran perfectly. before the second time out i had pulled the supercharger out and just replaced the washers with steel (riva) washers and new needle bearings, put charger back in and did an oil and filter change with the new oil from seadoo, (synthetic blend) and changed the spark plugs, the boat did not come with an hour meter, so i installed an hour meter and have put 8 hours on boat since, I am going to replace just the oil again when i get to about 10 hours or so, just to keep the charger happy, I think after reading alot about the charger that it is in your best interest if you have a charger to replace the oil a few times throughout the season to keep everything clean and lubed, and that will help with charger failures. I plan on pulling charger before next season and doing a complete rebuild to 08' spec's and then just doing a couple oil changes throughout the season again, keep your oil clean and i dont think you will have any problems with the charger, rebuild it once every 100 hours or less and power on.