I have a 2004 Sportster 155hp and have not had any problems with it. Bought it used and the only thing I ever needed to do was rebuild the jet pump due to lack of maintenance from previous owner. The 155hp non-supercharged engines are just about bulletproof if proper maintenance was done, and with only 60 hrs it should be in good shape.
As far as the engine goes, you will want to make sure that the oil, coolant, and spark plugs have been changed regularly. You may want to have a compression check done to each cylinder to ensure the engine is in good shape. There are no known problems with these engines, the early supercharged engines did have some problems related to the superchargers but thats it.
If possible you should test drive the boat (in the water) before you purchase to ensure the propulsion system is in good shape. At this age it is not out of the question for the jet pump to need service. The drive shaft seals, impeller, wear ring, bearings, etc. may need to be serviced. A good check is to get it out on the water and make sure it drives well and there is no cavitation with the propulsion system (easier said than done in the winter). As far as speed and power I can get low to mid 40's out of it. On the best days with only me in the boat I have hit 50mph. I can tow 2 tubers and skiers with no problem and these boats are just fun to whip around. I am really happy with mine. Sometimes I wish I had a bit more power, but I am also thankful I do not have to deal with the supercharged engine; something to consider.
The hull of these boats really have not changed in the last 10 years. There have been some minor changes to the helm, gauges, etc., but nothing below the water line. Since it is being sold by a dealer I would hope the boat has be thoroughly checked over, but you can never be too careful. Since it has low hours, the boat has done some time sitting around. Sometimes things fall apart faster as they sit rather than if they were used regularly. If it was stored properly there should be no problems, but take a good look for corrosion in and out and that all the electronics work (including gauges).
Not sure how much you know about seadoo boats, but they are fairly simple to work on if you have if you have even the slightest mechanical ability. This forum is filled with info, so search the threads if you are curious. Hope this helps, post back if you have any other more specific questions. Good luck with the purchase!
