Hi, all! First, I am by no means the world's most technical boater! I will try my best to describe my problem in as much detail as possible. We have a 2003 Chaparral 265 ssi with the 8.1 volvo penta. On Sunday, while preparing her for an afternoon cruise, the boat started to shake violently from side to side with the engine running at idle. I immediately shut it down, opened the hatch, and started it again to take a look and see if I could visually identify any abnormalities. What I discovered was what seemed to be the steering actuator at the back of the engine vibrating violently. Oddly enough, I turned the wheel rapidly and it completely stopped. Turned the wheel again in the same fashion and it began shaking again (this shaking continued on its own until the engine was shut down). It seems obvious that there is something up with the steering pump/actuator. I'm not sure if anyone could shed any light as to what it might be or any repairs we as the boat owners could do to fix any problem. I have not seen any leaks in the bilge and the steering had been working up until that instant. Anyway, thanks in advance! Have a great day!