317 is shaft drive with horizontal crankshaft. No way to remove the blower housing without removing the engine on this series. I would recommend taking out the spark plugs so you're not fighting compression, remove the front grille, and put a wrench on the PTO clutch bolt and gently rotate it to see if you can turn the engine. Dont put too much pressure on the bolt. We don't want to loosen it. We just want to see if the engine moves. It should take much effort unless something is stuck. Or put a pipe wrench on the driveline under the tractor between the engine and transmission and see if you can turn it that way. Once you verify the engine isn't locked or bound up, we need to diagnose your starter circuit. I've seen a worn starter bendix get bound up against the flywheel ring gear, but from your description, you may have something else going on. We just need to make sure the engine isn't stuck first. I know in the 318's, which have Onan engines, you have to pull the engine to get the starter off. I'm thinking the same may be true with the 317 as well since it's similar to the 318, but without power steering. Let us know how you make out.