Minn Kota Maxxum trolling motor seems to have lost thrust

My TM has worked great since I bought my boat last year (used) but the last couple of fishing trips I noticed a pretty big reduction in the speed that the motor would move my boat...the variable speed control works if I take the prop out of the water (prop will spin faster at higher setting) but when the prop is in the water it seems to have trouble going any faster than about 1/3rd normal speed than I'm used to.

I have already had the battery tested at two different auto parts stores (load tested) and it's showing good...I also thoroughly cleaned the battery terminals and wire connectors with wire brush and sandpaper. I removed the prop and made sure there was no fishing line or debris and everything looks clean. I also cleaned the male and female ends of the plug connector at the bow where my foot pedal connects...nothing has gotten it back to normal yet.

The only thing I noticed is that the pin through the spindle (pin-drive) that you seat the prop on to is very slightly bent but not enough to look like a problem to me...like I said the prop spins like a champ out of water but not in the water.

Any advice on what should my next steps be?

Thanks