A Snarkling gets out her yardstick:
Is it true that there's no point in querying a mainstream fiction manuscript that exceeds 100,000 words? Mine is currently quite a bit longer. (180,000) I don't think there's much fat in the story. Should I cut, quit, or query?
That's one big novel there!
Does it fetch and roll over too?
There are sweeping sagas, and huge novels published these days. Not many, but some. There was a story in the Times recently about a book that weighed over five pounds, and the author's website (tongue in cheek) offered "safe reading positions" for the tome.
My limit is about 100,000 words. I'm not a fan of sweeping sagas, and I'm not much on needing a trolley to whisk the manuscript off to an editorial lunch. Trolleys so seldom match one's shoes.
But, this is your work, your vision, and if you think it's at the correct weight...err...word count, then by all means, stand by your man.
Look for agents who have represented big books previously. Some of them love the darn things.