2550 oversteering

Hi,
I've set up my 2550 in Mixed A&B, open loop mode for differential motor steering of an autonomous boat. The boat steers well in manual RC mode. When switched to autopilot mode, it sometimes cant decide what to do, other times it steers well. It is using a GPS for autonomous navigation - the autopilot does have a gyro. When turning to a new heading in the automode it sometimes finds itself running in circles - forward and backward, and when on course does, at times tend to S - turn. I'm not quite sure if I want to adjust acceleration,the control curves or the left/right parameters. Any suggestions before I begin changing parameters would be appreciated. Thanks.

<P style="MARGIN: 0px">I have no suggestion. I can only affirm that the controller works identically in RS232 and RC mode (i.e. same acceleration, command curves, left/right adjust, ...). The only thing that is different is the command deadband that does not exist in RS232 mode.
<P style="MARGIN: 0px">
<P style="MARGIN: 0px">What changes, obviously, is the way that the command is given to the controller: in RC mode, the joystick min and max positions will create a command value of -127 to +127.
<P style="MARGIN: 0px">
<P style="MARGIN: 0px">In RS mode, you send the command values explicitly.
<P style="MARGIN: 0px">
<P style="MARGIN: 0px">

Cosma,
The autopilot is uses PCM when in automomous mode. RS232 is never used.