No single source. Top Speed and Boat Test websites have done reviews of several models, and you can find some info there. Good news is that from 03-08 you are basically talking about 3 models for Yamaha (VX, FX, and FX HO). They all 3 use similar non-supercharged engines, and are all reliable. In 08 Yamaha made some changes, and went with a totally different engine for the FX models and added a supercharged option on a couple of skis (SHO and FZR/FZS). If you have a specific ski or skis in mind, post back and someone can give you all the specs. I have the numbers on all the Yamaha 4 strokes. Reliability is not much of an issue on the non-supercharged engines. The supercharged engine models has added a few more headaches, but Yamaha still leads the industry in reliability.
Also I'd recommend avoiding a 2 stroke ski...............you will save yourself many headaches.