Here's my write-up on your starter motor. CLICK HERE
It's true that your charging voltage can be ~14-VDC. The battery settles down to 12-VDC. While cranking, especially on an older battery, voltage can drop to 10-VDC BUT your engine should still start just fine.
I know of folks who bought a brand new battery that had a cell shorted. They ran with it for five years without realizing because most cars don't have a volt meter and BTW, who checks? The way they found out was when they replaced the battery with one that fired on all six cells. The difference was amazing. - Dave