Even though the wheel is SS it can still cause deviation in the compass if to close due to the rotating mass or possibly due to the other metals behind the wheel.
On my last boat my compass would change by 10 degrees when I turned on the blower and bait pump at the same time. The compass was about 4 inches from the top of dash.
Compass placement is very critical yet most boat builders give it no thought. :-[

CBuzz