I have the same issue, need to do the same thing... you need to pull the entire lower, should I be doing something with impeller? greasing something? checking?
Remove the cone on your pump while it’s out and change your pump oil. Remove cone -3 bolts drain gear oil. Check cone o-ring. Put cone back on. Remove set screw. Fill with gear oil . 80 wt I believe. Allow it to burp several times to get it full.
Most likely your carbon ring is worn causing your leak. Replace with a new one. Make sure your rubber bumpers are on the ends of your drive shaft when u put it back in as this is what holds pressure against the carbon ring keeping water out.