We purchased a Raymarine autopilot (used), and spent the season last year calibrating and recalibrating it. When engaged it steers our boat in sinus curves with ever increasing amplitude and increasing violence. Very scary.

Raymarine has not responded....

Alex,
We had all manner of curious similar gremlins with our Raymarine pilot. They started when it was about 4 years old and were completely unpredictable which made them both dangerous and annoying. I think John Franklin had similar problems with his. He solved his by replacing the memory chips. We eventually sent ours back to Raymarine and they re-programmed it. Ours has been OK since then but we are keeping our fingers crossed!

The problems we encountered were:
1. Suddenly and unpredictably disengaging
2. Misinterpreting heading data from the compasswhich caused it to lurch off course. Often it would think that our heading would be up to 180 degrees out!

My guess is you have a corrupt software issue.

Simon

Interesting you should describe that problem - a friend n Mexico has just told me of the identical scenario... Must see what I can find out.
Which AP exactly do you have?
Cheers, J.

Ours is the sp-70 with the ST 7002 head circa 2006

FYI…
Alex finally managed to get an answer from Raymarine through our friend Will Sayer who works for them. It turns out that Raymarine autopilots have an internal gyro that whigs out on occasion. It is a known problem. They sent us a complex series of diagrams about how to open the machine and disengage the gyro. Meanwhile, Will suggested we just send it back to them to have their techs do it for us. As it turns out, there is a standard charge of £40+ for simple diagnosis of the problem and more than £400 for any repair, which has to be paid up front. That was great incentive to attempt the job. Alex was successful and we finally have an operational autopilot. If anyone else has this problem, please let us know and we 'll share the diagrams (which are hand drawn by the lead tech and hard to decipher but they worked).

Vice Commodore, OCC 

That 's great news. We paid up and got Raymarine to sort ours out.

We have a new electronic gremlin today! We are on passage to Argyll and have on Tacktick repeater telling us we are doing 9 knots and another telling us 24 knots!!!!. Not sure how that is going to effect our logged distance! Some more calls to Raymarine I think as they bought Tacktick a year or two ago.

Simon

Hi Simon
when you find out why this is happening, please post it. We have a similar issue(s), though we use our chart plotter trip log for the mileage.

Our chart plotter (Northstar M120), our Raymarine Autopilot (ST3G), and our Tacktick wind and speed instruments and all interconnected (as is our Icom VHF and AIS transponder).
Our chart plotter will (for example) show a SOG of 7.5kt, the Raymarine display shows 6.9 as 'speed ', while the Tacktick shows 6.5kn (through the water).

Just to add to the interest, while at anchor (0kt speed) the Tacktick will display two different wind speeds and directions for apparent and true.

Hello Daria

We had similar problems with our Autopilot ST6001 last month - veering to port in an increasingly sharp curve, and reading 180 out. We tried to correct the reading by doing the recommended slow circles etc but the result was an error message reading Current Limit, and the autopilot then refused to engage. We made numerous phonecalls to Raymarine but we still couldn 't solve the problem. We concluded eventually that the fault lay in the course computer, which we have removed and sent off to someone in Ardfern who is said to be a Raymarine agent. We haven 't heard back from him yet.

We would be really interested in a copy of the diagrams if you think they apply . We have a friendly marine engineer who might be able to do it for us - for less than £400!

Thank you.

We had one episode of aberrant behaviour from our Raymarine when it decided that our heading was 180 degrees from our COG! I went below and thumped the fluxgate and unbelievably it did the trick! Never fixed any misbehaving electronics with brute force before.

Just in case this was luck and proves to be a temporary 'fix ' I 'd be grateful for Daria 's diagrams too as we have a gyro too
.
Simon

Hi there
As it turns out our problem was 'fixed ' by disconnecting the internal Gyro. This is not saying that this is a universal solution. it worked for our STG3 course computer.

I have attached several files for you to review:
Raymarine STG3 repair: this is a synopsis of emails from the tech at Raymarine when we narrowed our problem down.
Fluxgatetest: do this before the prior doc (this one is for Simon)
Rudderrefferencetest: do this one first

Carolyn: friends of ours also had a voltage problem. On investigation we found that the 'professionally ' installed power cable was way too small and that there was a significant voltage drop. There are charts available that show voltage drop based on power consumption and cable length/diameter. With a big draw like an auto pilot,always go a size or two bigger - (just like you would with an anchor ;) )