I believe you need to adjust the "rudder gain" down, the default is 5 on a 1 to 10 scale. You can do it temporarily by pressing two buttons I can't quite remember right now.
You can also do it permanently by going into the calibration mode. For wheel
steered boats with fewer than 3 turns lock to lock the recommended settings are what is known as "The Catalina
Cocktail". Mainly because there's less than 2 full turns lock to lock on many of the 3 digit boats that means the default settings oversteer and overcorrect. The following is from the Raymarine
tech forum regarding these toned down settings.
Optimal setup for the ST4000+ on a Catalina 270
I have a ST4000+ wheelpilot
I recently installed on a Catalina 270 sailboat. At the West Coast
Catalina Rendevous the Raymarine
rep said that you guys have some recommended default settings that work best on Catalinas. I'm having trouble getting the autopilot
to track well, even with the rudder
gain at the lowest setting. The boat has a tendency to oscillate. Can you supply me these recommended setttings? Thanks.
This boat has a relatively low number of turns on the wheel from lock to lock. I would recommend you change the following setting from the default in this order. Please do these one at a time while evaluating performance after each change. Also, make sure that you have gone throught the compass
linearization with a deviation of 10 or below.
1. Change the Rudder Gain from 5 to 2
2. Change the Auto Trim from 3 to 2
3. Change the Response from 1 to 2
4. Change the Drive Type from 1 to 2
Please avoid changing the drive type if possible. If the turns on the wheel from lock to lock are less than 2 then you might try the Rudder Gain at 1.
Here's the st-4000 manual online:
Chapter 3 describes the effects of rudder gain and adjustment.
And if that's not the right one this page has all the "legacy" model manuals