F115 code 28 revs limited to 3700

[FunkyDubz.com]

Hi I have a 2002 F115 4 stroke with the flashing 28 code and restricted revs at full throttle to 3700 revs, runs perfectly otherwise.
My thoughts are shift position switch restricting revs as it believes it is in neutral, if I correct is the switch adjustable or will it need replacing, if it needs replacing will it need a diagnostic reset or will it plug and go?

[boats.net]

Check shift cable adjustments on engine, adjust as needed.