Nav Pilot 300 deviates bad under way

[Fishing4kooks]

I had a successful calibration and I have an accurate heading with the pg700. The nail palette seemed to work fine for the last two weeks. I’ve been in the water. But recently underway at cruise speed I’ve noticed it deviate portside very badly enough where it sets off the alarm or will constantly be correcting itself. It’s becoming really frustrating. My mounting position for the Compass is good and was working just normal for the first couple weeks now this sudden change.
What should I look at? This is my first auto pilot set up I’ve done on my own.

 

[Bayhouse]

Has anything metallic been moved to nearby the compass?

With the AP controlling the boat, I'd keep a close eye on the COG and HDG readings to see if they're different.

I would do a factory reset and redo the calibrations as a start.

 

[Fishing4kooks]

Has anything metallic been moved to nearby the compass?

With the AP controlling the boat, I'd keep a close eye on the COG and HDG readings to see if they're different.

I would do a factory reset and redo the calibrations as a start.

No nothing is near the compass at all. The COG and HDG are + or - a couple degrees at any given time.

 

[TheReaper]

If the heading sensor is working fine, then I would recommend using a Power Purge system on the hydraulic system. There seems to be air or something in the hydraulic system that needs to be bled out.