I took a look at the save and found that if you first ungroup the 3 ships, you will notice that the "no cavitation" option is checked for the ships.
Seems like it might be a bug, since as long as the ships are grouped together, the no cavitation option is not checked, yet the ships are acting as if it is.
If you first ungroup the 3 ships, and then uncheck the no cavitation, and then regroup them, you can increase their speed up to 35 knots.
**EDIT** I just wanted to clarify that you have to ungroup the ships using the 'D' Detach function. If you just go to Unit View the ships still won't have the no cavitation option checked. Once you 'D' Detach them, then check their throttle settings, you should see that the cavitation option is checked.
< Message edited by kholdstayr -- 1/18/2020 7:41:02 PM >