Silent running does more than just reduce your speed.
It turns off bilge pumps, trim pumps, any other non essential machinery. Your crew will also put their slippers on.
So - turn on silent running. You can then change speed.
You will still be in silent mode, and quieter than a boat doing the same speed in normal running mode.
Don't forget to turn it off again when you need to reload your tubes.
But if you are being hunted you really don't want to be reloading. It is very noisy.
Hope that helps
