not too sure what kind of steering system you have, but there may be a threaded adjustment where the steering cable connects to the "tiller" linkage... if so, you may be able to disconnect it there and then the wheel should turn stop to stop with out any problem. if it does, then place the wheel at its center position..... then center the rudder(s)..... then with everything centered, screw the adjustment in or out as needed to make the connection again... if there is not enough adjustment, then you may need to modify it to get the proper adjustment.
sometimes there will be a combined adjustment, one at the cable housing end where it anchors, and a threaded adjustment at the "tiller" connection... if so you can work them both to get what you need.
if the wheel is out of position when everything else was correctly positioned, then the helm would have to come apart to adjust the rack and pinion..... but usually this is never the case.