The plot thickens.
Two possibilities here:

1) The shaft was aligned a little off the centre when is was set up (but still correctly aligned). No worries there.

2) The impact moved the strut or bent the shaft.

If it is the latter they may be visible stress # in the gelcoat around the strut mount. Look there for damage. If there is no damage then try rotating the shaft by hand (boat in neutral, motor off! cutlass bearing wet. There should be no binding. The shouldn't be a point during the 360 degree rotation that the shaft seems to hang up. You are into professional repairs if there has been any movement of the strut.

Have you had a chance to try a good prop and to check the prop is seated on the taper or alignment at the flange yet?