I have a 1973 25 hp evinrude and a 1978 70 hp evinrude, I havent been having any problems with them, but I have had them a couple years and dont know the last time the impellers were changed out. They were checked by the mechanic last year and he said they seemed to be moving water fine. But I would like to change them out during down time this winter. I see that I can buy just the impeller or the water pump repair kit that has the impeller included. Should I just replace the impeller or are there parts in the water pump kit that should also be changed out because Im not sure how long its been since the impeller has changed or if it has ever been changed? Thanks in advance for the help!