Deejay, I wonder if that mower has no drive to the rear drum? I agree with you that propulsion plus grass-cutting from a half hp motor over a 17" width sounds a lot to ask. I suspect the propulsion takes more power than the cutting wtih a reel mower, so if a previous owner put that little motor on it but also removed the drum drive, it might be a more or less workable tenant's improvement situation.
What we really need is a picture or two, so you can compare the mower with yours.
