Evan,
I can't answer your question, but it sounds sort of like the syatem that was
on our 35 ft cat.
Tillers connected to a "traveller" car by a two cross bars, one to each
tiller. The traveller car was pulled to either side by the cable and drum
steering.
The tiller pilot was connected to the steering traveller car, so could still
be used if the cable broke.
I suspect tiller pilots use less power, if that is important.

"Evan Gatehouse" wrote in message
...
Does anybody know how long a typical hydraulic outboard steering cylinder
lasts in salt water usage? I'm wondering about using one with a hydraulic
autopilot pump - read on......

I have a 40' catamaran with an ususual steering system:

The rudder stocks are external (hinged at top of the transom) and are held
down at the bottom of the transom with plastic collars and rope. This
provides a kick up facility.

There are external tillers on tops of the rudder stocks. There is a
external crossbar to link the tillers. To steer the boat, there is a
tiller extension linked to the cross bar. There is also a rope steering
system with ropes/pulleys/a rope drum - wheel arrangement that mostly
lives under the bridgedeck. It's all very low tech but simple to fix.

Now I am going to take this boat offshore cruising and the choices of
autopilots include:

- tiller pilot type like Autohelm 1000/2000/4000
- wheel steerer like Autohelm 4000
- maybe a hydraulic pilot with an external cylinder.

The helm loads are very low. Totally balanced helm. Existing pilot is an
Autohelm 1000 that copes very well, but has only seen 4-5' seas upwind.
Reaching at 25 knots of wind, full sail, and you can still steer with the
tiller extension and only very mild weather helm (with a 3-4' tiller).

My current thought is a 4000 type pilot cause it's cheap and I have the
1000 tiller pilot as a backup. I know it won't last forever, but there is
a 33' cat that has been using one for a few years and it's still going
o.k.

I am looking forward to being inside the saloon on a rainy day, pushing
the buttons on the remote to steer the boat

Evan Gatehouse