Steering Adjustment

Replaced my steering cable last season, as the old one siezed up during winter storage.

Run my boat on 4 miles of the estuary on the River Severn in U.K. , which is about 50-60yards wide.

I adjusted the steering as best i could to get equal movement in both directions, but still could not turn at even 18mph where the river was narrow, as the rudder only had about a 90 degree movement (45 degrees each side of centreline).

So turning was a problem last season, i only turned at the end of our boundary where the water opens up to about 80-90yards wide.

So, as a winter job this year, i relocated my steering cable pin on the rudder drop arm, so that it was closer to the rudder centreline of turning.
(basically i drilled a new hole closer to the rudder)

Now i have full travel of the rudder, but have noticed that the steering cable can almost touch the rudder centre pin.

Is there a method of installing steering stops or limit pins?
Has anyone seen this before.....?

What is the normal turning circle of a Moomba Mobius?

I am running a Mobius V 2000 with an older Teleflex type worm steering setup, not the new rack and pinion type.