I have a 1996 SeaDoo GTS, this thing has always ran fine, I stuck it into the river and drove it for an hour or so with no problem. Then at full speed it started slow down, I gave it full thortle and it wouldn't go very fast. It stalled. As soon as I started it up it ran for a minute or so at full speed then the speed would die back down. IT kept doing this. I did have new plugs installed which looked fine, the battery is new, I put new fuel in which was mixed with some old fuel I had in there which was about a gallon. I pulled the fuel filter off which is located underneath the the hull and that was clean just a little debri in there. This SeaDoo kept stalling though and would never get up to full speed. Not sure what's wrong since I've never had this problem in the 10yrs I've owned it.