[hiccup]

What you're describing is 100% normal for a twin-screw inboard boat. If you go nearly hard over on the wheel to starboard with only the starboard engine in gear, you should be able to maintain a straight course. Your ability to actually turn to starboard will be greatly reduced though. As an example, for my boat when there's only a single engine in gear, I need to maintain the rudders at about 70% hard over towards the engine in gear just to maintain a straight course.

This is because the starboard propeller is off center and therefore pushes the boat to the port, and vice-versa. This is why twin-screws are so easy to maneuver with just the gear selectors and can spin on a dime.