Hallo Jail
It's 'common knowledge' that many of the internal gauges in SH3 show wrong values sometimes, but I haven't noticed the engine dial in the sound room to be wrong. At least not with the XXI, where the engine dial is clearly visible when operating the hydrophones.
But I haven't checked in other boats. What boat are you using?
And I know that the World mod (and some other mods) will sometimes cause all of the needles to point up on the internal dials, but I didn't think it affected the engine dial.