|It probably depends on what the covers are made of, but I did it last year and they came up bright and clean, without shrinking.
I suggest you mark all covers and foam 'innards' ( good name) when you pull them apart as I had a bit of a battle matching them up last time!! My innards were wrapped in thin plastic sheeting to keep them dry even if the covers were soaked by wet gear, spilled drinks, water through the companionway in heavy weather etc etc. You will be amazed what a pile of material is involved, several home-sized washing machine loads unless you go to a laundromat with commercial sized units.
Alan of SMOKE 1984 Mk V 002