ford 800 tractor wont start

I have a murray 11hp tractor, it was running then I turned it off. I went to go and start it back up but no luck. Didn't even to nothing. I purchased a new battery, key start and no luck still. I think previous owner did some wiring of his own on it.

I have a craftsman tractor from the mid 90's with the kohler 15.5 hp motor. It won't even turn over, I've checked the starter/alternator, and just replaced the ignition switch, the deadman seems to be engaged, brake/clutch were working last time I used it, the blades are in the "dis-engage"...

I have a ranch king riding mower. It won't start. Had starter checked. It is OK. How is wiring run from battery to starter to bypass all the safety switches? Is it negative to ground and positive to starter with maybe a toggle switch to break the current to starter?

Last year I bought an old Wizard riding lawn mower. Its got 12hp, 465 cc, and 38 inch cut. It ran great until, I was mowing, hit a rock, and the mowing stopped there. The battery went dead, so I've replaced that. Still nothing. Where should I start, to get it to start?