Motor guide prop adaptation

The prop on my bow mounted trolling motor (Motorguide) is getting pretty long in the tooth however the motor is pretty old (probably made in the early 80s) and I'm not sure I can even find a model number on it (it was given to me).  Anyway, I ALSO have a transom mounted Motorguide which came with a spare ("weedless") prop.  It seems to me that with a plastic sleeve or spacer, I can adapt this spare prop for use with my other motor.  The prop itself looks to be slighter larger in diameter but the sleeve fits over the motor pretty neatly.  Are there any pitfalls I should be aware of (such as ruining the motor) before attempting this project?