Ballast pump problems

Hi,

Last season I had to replace my impeller on one of my factory hard tank ballast pumps. They are Jabscos', and replaced with a jabsco impeller.

I compared the original impeller and the new one, and they looked exactly he same.

Changing them was pretty easy, just drop the new one in and spread the supplied lube evenly on the impeller.

But since then, that pump works slowly, and I can hear the motor run harder and it get stuck in fill or empty position. I have to play back and forth with the switch and it would eventually change position.

Anybody with the same problem? How to solve this?
If it is a lubrication problem, wich one is recommended?

Thanks