Servicing and fine-tuning AutoNav PF 0.3 SBP pumpset

[masterov]

I am going to leave the part numbers here (PF3SBP-12 Part # 23170-21 with RFU-25 Rudder Feedback Unit) for easy searching, but I am guessing this applies to almost any pumpset. The specific pumpset I am talking about is made by AutoNav and works together with a Nexus autopilot.



The fluid in the pumpset looked darkish with some residue, and there was very little of it in the reservoir, so I decided I needed to change it.

At first I drained the old fluid. This was relatively easy. just unscrewed these hoses:



The only trick was to drain the reservoir below the intake line. I had to unscrew the pump to be able to lay it on the side to drain all residue from the reservoir.

Then the question was: what do I put back into the system. A few people suggested ATF (automatic transmission fluid) for its good de-greasing qualities, so that's what I did.

Now I had to drain the air from the system, so I followed the instruction manual and steered the system from extreme right to extreme left several times by using the "power steering" mode on the auto pilot. This presented a bit of a problem. Air compresses well, so when I reversed direction, the ATF gushed out of the reservoir. Eventually I figured to do it in small increments, and was able to drain all air from the system.

At the moment, even though my system is calibrated so that 0 on the instrument corresponds to the 0 degrees rudder, when I steer to extreme port using power steering - it only goes to like 36 degrees, and if I go to extreme starboard, it goes to 45 and doesn't stop there (the motor continues to pump) even though the rudder has reached its limit in turning point. This causes pressure to build up, and when I reverse direction, the pump set spits out the ATF from the reservoir.

I believe this has to do with how the RFU was installed. Should I adjust it and re-calibrate in order to balance port and starboard extreme points? Has anyone had a similar problem? how did you solve it?

[DeepFrz]

There should be a way of setting steering limits in the autopilot setup. This is a link to a Raymarine setup procedure but you will likely need to get the manual for your system. It may be online.
http://www.raymarine.com/uploadedFil...utionSetup.pdf

[masterov]

Thanks. I'll try to find out if Nexus autopilot allows it, and will report back.

[masterov]

Thanks @DeepFrz, you were absolutely right, I was able to set the steering limit to 35 degrees. I don't think an auto pilot would ever need more than that, and that definitely solves the "spitting" problem

[DeepFrz]

Great. Happy to help.