My aft cockpit covers (canvas & plastic ) are covered in salt & diesel exhaust . Do you think they could be washed in domestic washing machine or maybe the marinas launderette without damage to either.
Well I'd be surprised if it would fit in! Ropes are ok in washing machines and some Bounce works as well, but cant see you getting much tumble action with the washing machine stuffed full of cockpit cover.
NO - don't do it.
Go to your local Caravan Showroom and ask for an AWNING cleaner. They are specially made so that they do not destroy the Waterproofing element in the cloth.
Use a soft nail brush and all will come clean.
On the plastic one use a stiff nail brush and use JIF (or CIF) or whatever they call these days. That should work IMHO.