Bliss, there is ComNav and WH-Autopilots (has good reviews
on this forum). There is also Simrad
. That's just a sampling, but probably the most common and well known.
WH seem to be the simplest but quite robust. The things I don't like about WH is the pump is belt driven and it looks like it was built in 1960. I don't know for sure if those are bad things, just some things that make me wonder.
ComNav seems to have a good customer base in the fishing
fleet and larger boats.
has large install base.