Outdoor Power Equipment and Small Engines - Lawn Tractor won't turn over

I have a Mastercraft (probably made by MTD) 14.5 lawn tractor. When you put the key in, turn it while pushing in the clutch, all you get is either a click, or a whine noise, or the flywheel will attempt to turn but stops right away. We have charged the battery on two occasions to get it going. After that charging it did not work. We then boosted it which worked two times. We now have bought a new battery...of course that didn't make it work. The next day we installed a new solenoid. It fired up right away and I cut the lawn. Today it's not starting again...same symptoms..except no clicking..I get the whine noise with the flywheel turning 1/4 turns then stopping. Should a flywheel spin freely if you turn it by hand? Mine does but gets stuck at a certain point so you have to press down a bit harder to get it past the sticking point. Also in the last couple of days the tractor moves freely with the parking brake on/ or while in gear. I'm trying to find all the safety interlock switches but my manual is the pits for stating where they all are...specifically the clutch-brake pedal one. Can anyone tell me where I should look for this?

The whining noise is likely a stripped starter gear. There is a black cover over the gear held on with two small screws, remove the screws (1/4" wrench or driver needed) and inspect the gear. It is "plastic" and is fairly simple to replace. As far as turning the engine over by hand and getting "stuck"...you're at TDC of the compression stroke and will require extra effort to get past. This is normal. Another long shot possibility for the spinning-over trouble is that you may have a defective Mechanical Compression Release (MCR) mechanism on the camshaft. One step at a time though...check the gear first! As for the brakes, an adjustment is needed it sounds. With a 1/2" wrench, tighten the center nut on the brake arm on the tranny until it's suitable pressure for the weight of the machine and rider to stop it.