Auto Pilot

During our winter cruise of the Caribbean in 2007/2008 we had trouble with our B&G Autopilot. The Autopilot system included the ACP-1 computer, RAM T-1 hydraulic RAM, and RRU-1 rudder reference unit.

After the autopilot had been on for several hours it would fault displaying “RUD DRV”.  I verified that the rudder reference unit was sending rudder position information to the Computer so I was reasonably sure that the problem was with the hydraulic RAM drive motor or valve assembly.  I removed the RAM and sent it back to Navico NW a

nd after a month or so I got the “repaired” unit back. Looking at the drive it did not appear that anything had been done but I was charged for the repair.

On our return to the boat in the winter of 2008/2009 I reinstalled the RAM and had the same error as before “RUD DRV”. We suffered along without our trusty autopilot for the rest of the winter and I made the decision to try and replace the RAM with the Raymarine M81131 type 2 short linear drive. I chose the Type 2 drive based on boat displacement but purposely went a bit oversize.

My decision to go part way and replace just the RAM with the Raymarine Linear Drive was based mainly on the premise that if the replacement of the RAM did not solve the problem then I would probably go ahead and replace the remaining B&G autopilot components with Raymarine components.

New Ray Marine RAM
Old B&G Hydraulic RAM






Comparison of the old drive to the new Raymarine drive showed that it would fit in the current space but I would have to redo the mounting plate and mounting location and also reverse polarity of the drive motor wires so that the drive direction would match that already setup in the B&G Computer. Since the Raymarine drive provides approximately 2 additional inches of movement I also wanted to adjust the mounting location on my drive quadrant.

I drilled a new hole in the drive quadrant at approximately 10” from rudder post center and the RAM travel to end stop settings were verified. I fabricated new mounting braces from ¼” x 4” aluminum plate.  Just in case the new drive hole was not correctly located I drilled another midway between the original hole and the new one.

Original drive hole on the right – one new hole to the left and just in case hole in between these!  I did not have access to a drill press in Grenada.
Steering quadrant end – as originally drilled for B&G
hydraulic RAM.

The big test – we shipped the new RAM back to Grenada in October 2009 and completed installation in early November. We checked the commissioning data on the B&G Autopilot and nothing had to be changed in the setup – the new drive is working better than the old (it is not dropping out) and uses less current!