there is a good guide available here

http://www.windpilot.com/

click on the "self steering under sail pdf file 7.4mb" link. Its
independently written and gives a very good overall summary of different
brands of self steering and their pros and cons. It doesnt seem biased at
all. Its not 100% up to date with the latest technology but it does give a
good overall view of self steering and might help you to make some
judgements. It is probably a bit more biased towards windvanes than
autopilots, but it has good info on both.

Shaun

My autopilot is an older analog type and it does not always make the boat
go where I want it to. It doesn't have a GPS input either. Worst of all it
doesn't give any kind of warning when it just 'gives up' in a sea it can't
handle, something that happens way to often anyway.

So time to upgrade. But I find that most autopilots seem designed for
smaller boats. I found some high-priced Furuno models that look good. But
before jumping in, does anybody have any experience choosing and
installing an autpilot for a 75ft 75000kg boat. One that then also worked
well...?

I'd like to re-use as much as possible of the existing installation which
is hydraulical and steered by solenoids, so I would prefer a system that
can drive most of that. Not sure if I can also re-use my rudder indicator?


Many thanks for your experiences, Al