boat off trailer
I knew a guy that had a roller trailer and he never allowed his bearings to enter the water. He would back it down to the edge only getting the tires wet. Off went the boat and loading it just reversed the procedure, winching it back on. He never had to do maintenance on his bearings and I was doing them twice a yr (I fished a LOT in those days).
If you think its not loading/unloading right, more likely than not you have it too deep in the water.