I would question other areas as well. If an owner doesn't maintain the rudders and strainers I would wonder how often he changed oil, coolant, transmission fluid etc. The others are right, replace them to be safe.
At least clean then to see the actual component, nobody can assess the condition behind that mess.
Sorry you didn't get the answer you were looking for. Thought about responding because I bought a boat and did a long trip early on and maybe had some insight. But given your post...have a nice trip. I hope it works out for you.