Ok, I checked the coupling. It's worn, but not broken. I'll replace that just for fun since I have it torn apart, but I don't think it's the problem. The clutch doesn't look excessively worn, no oil, very small amount of dust inside. The brake shoes don't seem to be hanging either. They seem to disengage completely when turning the cam.
So, I guess I'm not seeing anything obvious. One thing i did note is that the pump is a little hard to turn. The water drains though.
Any ideas? Could it be the clutch if I'm not seeing anything obvious there?