The fix is blowing in the wind
The right fan was sputtering - less than 700 rpm sometimes. It was loud and the body was getting hot. It was like there was a 2-stroke engine inside.
The repair was easy. I only needed to remove the battery plate, battery, 8 screws, and the back plate to access the fan. The fan came out after removing the 3 screws holding it in place and its power connector.
smcFanControl is a good app to monitor the fan speeds. It helped me diagnose the problem and verify the new fan works.