Ramosa,
We have the same boat, ours has the same problem in the opposite direction and has since I have been involved in the boat, about 2 years ago. We were under the impression it was because our Port Engine wear ring was blown out along with the starboard throttle required significantly more travel than the port side to maintain equal RPM.
I recently had both engines serviced to include new impellers, wear rings, replaced the steering cable, reverse cable and reverse cable pin. When I got it back on the water the problem still persisted except it no longer worsened with higher RPM, not nearly as prominent but still there, to include the the RPM disparity.
So I took it out again today to test and exercise the engines, now my starboard tachometer has failed and not functioning. Regardless, what I noticed for our boat was that if I maintain the starboard engine throttle farther forward of the port, my steering wheel straightens out and my steering is MUCH more responsive. While the boat still turns sharper and easier to the port side its much more of a clean steering response.
I spoke to my mechanic about it and he mentioned I could adjust my throttle cable to shorten the disparity but it might not be enough to completely equal them out and this should help on the steering wheel.
Have you had your wear rings replaced lately or checked your throttle cables for excess free play?
Not sure if any of this helps but I will be following your thread to see what others have experienced and I'll let you know if adjusting my throttle cable makes any adjustment in my steering wheel.
