Welcome to the forum!
Well, since being new to the forum and obviously new to the seadoo line of craft, it may take soem questions and answers, but eventually, we should be able to come up with some useful information for you.
You engine is the 787 Rotax, which is a very powerful engine. I think your system has the DESS (digital electronic security system). When you attach the lanyard, do you hear two audible beeps? Have you checked your fuel valve? Theres a selection switch for reserve fuel, on and off? What do you get when you try to start the motor? Does it roll over and not start? If so, have you checked to see if the plugs are getting spark? Have you done a compression test? Is the oil injection system still in place or did the previous owner already have premix started? Before I wait for the answers to all the questions, look inside the cover, you'll see an electrical box. Remove the cover, your MPEM (multi purpose electronic module) is in there. Check to see if any of the fuses are blown. Also, when you try to start the PWC, listen for audible beeps. Like I said, you should hear two beeps if everything is o.k. and ready to start. If you don't, I need to know. If you get more than two, count them and write back.................Hope to hear from you soon!.