(ET) Overheating deck motor

[Steve Gaarder <gaarder ecovillage ithaca ny us>]

We have a deck motor that runs, but draws a lot of current and overheats. 
I can think of two possible causes:

1.  Shorted armature winding(s), but we took it to a local motor guy; he 
put the armature on his "growler" and found no problems.

2.  Field magnets have somehow become much weaker - can this happen?

Any other ideas?

thanks,

Steve Gaarder