I was out and about and one of my neighbours had a 28 lb thrust motorguide t/m out at the curb we asked him if he was throwing it out and he said yes it isn't enough power for this big boat that he got..only problem is , that the prop has a broken blade it now has 3 instead of 4.  I am wondering if this will effect how it works.  I know props are fairly cheap but if I don't have to replace it why would I for the mean time.

Replace the prop.  A prop with a missing blade will vibrate so badly that it will jar the fillings out of your teeth.  In addition, it will place excessive stress on the motor bearings.

ok thanks...ill get right on it then.