The query letter itself will tell you if it's ready, in most cases. If the query is full of any extra wordage or bloat, then agents will assume the novel is, too. You will have an uphill battle to prove that the book is well constructed 
But to be dead honest, it may well get you instant rejected. Many agents auto-reject after 160k, some up to 180k. Mine will sometimes request up to 200k but she's never signed someone with that wordcount, and she says you can always tell in the first chapter if the writing justifies the wordcount or not.
If you really believe the book cannot be changed and wish to keep it the way it is, then it might be easier to put it aside and write/query something shorter, until you are more established.
But to be dead honest, it may well get you instant rejected. Many agents auto-reject after 160k, some up to 180k. Mine will sometimes request up to 200k but she's never signed someone with that wordcount, and she says you can always tell in the first chapter if the writing justifies the wordcount or not. If you really believe the book cannot be changed and wish to keep it the way it is, then it might be easier to put it aside and write/query something shorter, until you are more established.