CONTINUOUSWAVE

Q1: what error in assembly or connection of a SH5150P [probably means the DOMETIC SeaStar II SAFE-T No Feedback] rotary helm on a 13-footer with a transom support mounting kit (needed because of the curved transom) would cause the steering to move in the wrong direction?

BACKSTORY
I have a 13-footer. I mounted it [transom support mounting kit] on the port side and installed the SH5150P rotary helm with the cable holes facing port.

I tried switching the cable to the other hole, which fixes the direction problem, but it doesn't stay secure over time.

Q2: what is a reliable solution?

pv3 wrote:Q1: what error in assembly or connection of a SH5150P rotary helm on a 13-footer with a transom support mounting kit (needed because of the curved transom) would cause the steering to move in the wrong direction?

The typical installation is expecting the steering cable to installed on the starboard side of the transom. Installing the cable on the port side would invert the steering action direction, as you have discovered in your installation.


Fig. 1. The typical installation of cable steering on an older 13-footer with curved transom. The cable actuator is on the starboard side of the transom.

Looking at the installation instructions, you cannot randomly choose which port (“hole”) in the steering helm to fit the cable into. The port with the two-screw clamp is the port into which the cable must be inserted. The other port has only a one-screw clamp and is intended to only hold the cover for the center portion of the cable assembly which will extend out of the steering wheel mechanism as the wheel is turned. You should not switch the two ports because they are not identical.

The illustrations show a rear-panel view of the installation of the steering wheel mechanism with the cable connected to the top “hole” and the cable leading off to starboard.

pv3 wrote: I tried switching the cable to the other hole, which fixes the direction problem, but it doesn't stay secure over time.

This outcome is likely due to the use of the wrong “hole” for retaining the cable; the clamp mechanism on the second is probably not strong enough to retain the cable when higher force is exerted on the cable.

Turn the helm assembly upside-down from the way you have it now. Not that familiar but worth mentioning.

If you turned the helm upside down the steering wheel mounting point would be facing the bow. If you rotated the helm clockwise 180 degrees the cables would be exiting the helm but going towards the center of the boat.
I think you are on the right track with reversing where the cable goes into the helm, but you need to find out how that particular helm can retain the steering cable in the location usually reserved for the short tube that accepts the cable runout tube. I know the Safe T 2 helm allows you to insert 2 bolts to retain the main steering cable that goes to the engine in the position normally used by the excess cable runout tube. Let us know how you make out.

https://youtu.be/N8ZzaXHMV4Y?si=1ZcGk50ukcUXn2H6
This video shows how to reverse the direction on a Safe T II NFB helm.

The youTube demonstration (linked above) looks like a workable solution.

Does the manufacturer endorse that method?