I am a residental user and have an old murray mower that i was given. I had recently changed the oil and checked everything out and it was good. i had a bad battery which i switch out to a new one. i went and started it up and everything was running fine. I went to engage the blades and then i heard a clanking sound come from the deck i think. i thought i was the fly wheel but what happens is as i turn the key the motor spins but won't fully start or engage. i could be the flywheel key broke (this is an old mower). i am not sure. as soon as i let off the key the engine stops turning.