I'm not saying I'm right but I have never had to run the legs in beach mode...IIRC it should only be done in neutral my legs come up to 50 deg so i can inspect the props out of the water....
might be worth getting the bearings checked if you get vibration in "normal" running.....oh and assuming theres no bits out of the props
-------------------- I changed it cos it was too long....to drink and in letters :-)