First of all, check the voltage at the battery posts, then at the output terminal of the starter solenoid (the big lower terminal of the solenoid) and see if there's a difference in those readings. Quite often, slow cranking is a result of too much voltage loss before the current gets to the starter- - - - -bad cables, dirty connections, etc. If the voltage drops below 10 volts while cranking, try a known good battery in the circuit before condemning the starter.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!