I have a 1974 Cobalt 18' TriHull, 165 HP Chev, OMC outdrive. While running, it's hard to steer the boat to starboard (tight) and it wants to turn to port on it's own. It appears to steer fully from one side to the other.
Not sure if the electric shift Stringer has the ability to adjust the exhaust port on the cavitation plate behind the prop. On the later mechanical shifts with through-prop exhaust & most modern outdrives there is a small fin there that you can adjust from side to side to help deflect the prop wash slightly to offset prop torque.
Also, if you have trim, try trimming up some to see if that helps. If it does, play with the trim to find a sweet spot between maneuverability & performance.
If the boat pulls to starboard, move the rear of the trim tab to starboard. If the boat pulls to port, move the rear of the trim tab to port. If you only have power TILT and not Tilt and TRIM don't raise the outdrive when under way as you will take out the ball gears in the outdrive.
There are some reference markings on the exhaust port. One was longer than the rest and the exhaust was pointed more the port than to starboard. Thanks to the great info above, I moved it so it was a little more to starboard than the main mark.
SUCCESS!!! It works great! You point the boat in any direction and let go of the steering wheel and it keeps going.