It's been our experience that many boats are better on one tack than the other, remember that the molds were likely hand built, and anything may not be symmetric. But going all the way from weather helm on one to lee on the other is more than I've seen. Here's the potential easy fixes:
- The mast is not centered port/starboard - you can check this with a halyard and adjust your stays
- The weight is not distributed evenly port/starboard - is the thing listing, are there tanks on one side empty and other full, have you got heavy stuff on one side not the other.
- You are trimmed funny. Traveller, jib leads, something different one side than the other. You are trimming the jib in to tight on one tack, and the main on the other. Jib trimmed in will tend towards lee helm (pulling the bow down wind), main trimmed in will tend towards weather helm (pulling the stern down wind).
- Rudder not in the middle, not shaped the same on both sides, bent shaft
- Keel not centered, bent, etc.
- Hull shape from the factory not symmetric
- Mast not in the middle of the deck
It is not unusual on any sailboat to feel some side pressure on the rudder from propeller rotation...so I wouldn't worry about that.
Try the easy fixes first
Sabre's have a good reputation, I'd be surprised if this was a factory defect.