Not gonna be cheap!
http://www.johnsmcintoshvintagemercuryoutboard.com/Impellers.html
http://store.oldmercs.com/product_p/47-26554.htm
I also found an old iBoats thread regarding a Sierra 18-3008 impeller, which is supposed to fit except for the keyway, which could be modified to fit the Merc 250's key.
http://forums.iboats.com/forum/engi...impeller-47-26554-any-alternatives-or-sources
iBoats sells the Sierra impeller here, just search in Parts for the # and it'll pop up. I can't post a link directly 'cause the program is parsing even links from iBoats!!??
Last but not least, this guy takes your old impeller's brass insert and molds a nice, new rubber pump to the insert! He could probably do up one for a "Slinky" motor, no doubt!
http://home.earthlink.net/~flyingscott/
I have a Merc 250 hanging on the wall in the garage, haven't run it for a long time but years ago I replaced the impeller. Not exactly a fun job, but on the Merc 250 the impeller cup had the open end pointing downwards. The older models had the cup pointing up, and you needed even more special tools to get it apart.
The 250 requires a rod-like tool with a couple of cross-bent arms. I saw how the Merc tool was made and bent my own, it worked fine.
I've posted a pic of the special tool to my Flickr account, public view. For some reason I'm getting an error when trying to add the pic as an attachment. If you can't read it at Flickr, send me a P.M. and I can email the file to you.
https://www.flickr.com/photos/28953402@N07/17845448412/in/dateposted-public/
HTH & G'luck...........ed
