12VDC via robust jumper cables from a running Miata to positive lead on the starter and ground on the tractor (starter housing).

Is there any practical why to get a good/bad call on the starter motor before pulling the trigger on a replacement?

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1961 220b: first project car - sold.
2000 CLK 430: first modern Benz - sold.
2001 CLK 55: OMG the torque!!! - sold
1972 280SE 4.5: Baby Gustav
1991 300TE 4Matic: Gretel the Snow Bunny - sold
1978 300SD: Katz the Free Man - given away
1980 Redhead: Darling Wife