Problem with Sharp Autopilot

[alingher]

I have a problem with my autopilot and I hope that maybe someone can help me here.

It is a Sharp seapilot, which has a threaded rod (approx. M16, about 700mm long) with ball head accessing directly to the rudder quadrant. The installation is probably around 20 years old. The whole is controlled by a Raymarine unit.







In summer 2015 we once had a bit stronger wind (about 25kn) and a little bit more wave than usual (about 2.5-3m), where it could not hold the course anymore. It then did not work properly for the rest of the day. The next morning it seemed to have recovered and worked perfectly again.

This summer the pilot still worked well - except for the last day of our trip with again about 25kn of wind and 2-3m wave and swell. The pilot did not have enough power to luff over a certain point. I looked at the pilot more closely and noticed that the threaded rod still moved to a certain point, but then the motor just rattled. The pilot did not get particularly hot. After this, the pilot did not work anymore - even with less wind and wave. Unfortunately I cannot tell, if it has recovered and would work again now.

I have examined, cleaned and greased the thread. I could not see any defects in the thread and with the autopilot switched off the rod could smoothly slide over the entire length.

• What could be the cause of the problem? Could the electric motor be done? Is there a clutch that could be worn?
• How was it possible that the pilot could recover and work normally again?
• As this installation is pretty old, would you recommend replacing the Sharp unit with a new mechanical linear drive (Raymarine ACU 200)?

Thanks for any help!