All I want to do is sink your pretty ships...

[sergei]

Originally Posted by frau kaleun

I'm guessing I can switch back and forth between that and the other less specific speed dial in the same way I can switch between depth meter displays.

Yep that's spot on.
I'm going to guess from the way you worded your post that you don't know where the rpm gauge is.
Here is a screenshot, apologies if I am telling you something you already know