First confirm that the battery lugs are on the proper terminals. Red on positive +.... If so, you should take a look at the starter gear to ensure it is fine and whirring up into the flywheel gear.

The battery lugs are tight. Here's a little better description of whats happening. When I turn the key there is a click under the rear axle and then a whining noise coming from the same area.
Any ideas ?

First confirm that the battery lugs are on the proper terminals. Tight and on the wrong terminals doesn't help. I bring this up as some folks do not realize that the + terminal can sometimes be on the right or the left as the batteries are spec'd different. The click from the rear axle area is likely the starter solenoid. It has to be securely mounted. If all the grounds are good and the switch is sending 12v to the small terminal of the solenoid plus no power is getting to the starter- the solenoid is the weak link.

Hi, I think I've narrowed it down to the starter motor. Battery is new. Terminals are clean. Voltage is 12.8. When I turn the key there is a click from the solenoid. If I run a jumper cable from the battery to the positive lug on the starter the motor doesn't spin.
I can't find any instructions to remove the starter. I checked the service guide and the demystification guide. Can you help with removal/replace on the starter ?

Sure, could have a starter issue- but there are lots more unanswered questions here. I think you can have a couple of different engine choices that would affect how the starter comes off. A Courage has two little nuts that come off the top. Probably have to buzz out the 4 8MM headed bolts to pop the shroud first. The command has visable bolts. But before you throw money at a new starter at least test it using both jumper cables from a known good battery . Disconnect both terminals from the battery, hook the cable from the + battery to the starter lug. The - cable to the battery. Briefly touch the other end of the cable to the starter body- knowing it will spark, so use common sense and don't do this w/ flammables around. Can you turn the engine screen by hand? If you would like more assistance , post equipment #'s from below the seat or engine model and series #s and please indicate that you have followed the steps outlined.

Thanks for all the help. Replacing the starter fixed it. I was quoted $189 for a new one but ended up finding a used starter for $20 .

Nice!

Tob: Now That's What I'am Talking About :) !

Hi thanks for the post - maybi ask where did you find a used starter I have a similar issue and know it’s the starter. Thanks