I have a 1990 waverunner 500 just got it a few weeks ago. It starts and runs took it to the Lake today it was going fine then it slows down and would only go 5 mph. I also have a 1989 waverunner 650 it wouldn't run that fast also but I found rocks in the back after I got home. I was wandering if anyone can give me advice on what is wrong.