350 turns over very slow

If youre SURE the battery is good (try a known good substitute or have it load tested or jump it) and alllll llll cables n connections n grounds are good but she still cranks slowwwww ww, if you can get to all the starter/switch/solenoid connections using good tight heavy jumper cables without arcing or shortign out you may wanna by pass jump around the switch or solenoid n see how she cranks then to see if the switch or solenoid has a problem IE jump direct from the hot ungrounded battery post to the starter input (switch/solenoids output) n see if she cranks betetr indicating a bad switch/solenoid.

FINALLY if alllll lll cables n connections n grounds and battery n switch/solenoid isnt the problem, then I suspect the starter, ASSUMING the engine isnt bad or binding????? See how well she cranks with the spark plugs removed n no compression ???? Engines not over tight is it???

I ask all this cuz its often just a simple problem like a cable or conenction or ground or battery or switch/solenoid instead of a starter.

John T

A good set of cables for a tractor will cost $25., but will save big bucks on batteries and starters. I quite regularly get 5 to 7 years out of a battery, and last year I replaced a 6 volt after 13 years service in Canadian winters.