Lake Dumbleyung down east of Wagin would be a good place.
I haven't been there for years but they used it for speed boats & sking etc years ago. Doanld Campbell even ran his Bluebird speed record attempt on it back in 1964.
Theres a road to it on the North side. Kersley drive or sumit like that.
The lake is about 10km wide. Used to be fresh water but it's probably salty by now, like most inland water now is.
It would be more than 2 hours from Perth but if you're down that way it would be worth a look in.
In fact I will do it next time I'm down that way.