37kw isn't particularly big but it's near the upper end of normal electric motor ranges. There are also many variables, speed, frame size, winding arrangement, etc. Also check that the output shaft hasn't been turned down to take the impeller. If it has forget it as subsequent uses are very limited.
There are relatively few users of motors like this. OE manufacturers always use new motors so don't want it. Equpment users only rarely want replacements so buy infrequently. They can also have damaged motors rewound relatively cheaply without the hassle of removing your pump impeller. That way they get a guarantee and a motor they know will fit. Does your motor work? Unless you can guaranee that it does, no one will want to install it in a machine to find it's U/S. That costs money to do and possibly incurs downtime. I used to manage an engineering department in a large sawmill where we had motors like this. If I was offered one, I'd only buy it on the basis of a faulty motor that I MIGHT be able to get repaired. It would certainly get sent straight to the rewind company.
Basically, your market place is limited. Find out the scrap value and put it on eBay with that starting bid. Even then delivery costs may be a problem but you may get lucky.
John