Where about are you in florida? Lots of members there, maybe someone close by could take a quick look.
If the splines are worn at the engine side then the shaft won't be turning as it should. If worn at the impeller side then the shaft won't be turning the impeller as it should. it could be catching only a little bit. Replace it. How are the splines in the impeller?
PM minnetonka4me (in Minnesota) or his brother 99spxxx (in Texas)for used parts.