Hi hope you can help I have a 17.5 hp lawn tractor only 5 years old I use it for mowing and in the winter I have a snow plow on it this winter has been a bear I have went through three starters in four weeks runs like a champ then poof there goes the starter again I just get a click when I try to start it brand new battery had selenoid checked hope you can help starter runs 100 dollars and I am going broke on starters don't understand what could be happening

Starters can be tricky to install. You might need to shim it with metal shims to line it up perfectly with the flywheel. If it does not you could bust the teeth off or keep destroying the starter rod. This might be best left to a qualified mechanic to fix.

What is happening to the starter, is the teeth messed up, is it smoking, is it hanging in the start position with the bendix gear staying engaged with the flywheel or what?

Both guys ask good question and good pointers. I have a 4 year old 18 HP and never replaced a starter yet. Tell us exactly what failed on each starter, you probably have some other contributing issue.