do a voltage drop test on the starter cable
hook up 1 lead of the meter to the B+ terminal of the battery
hook up the other to the large cable terminal on the starter (the threaded post with alligator clips, not the cable terminal ring)

if the cable is good the voltage while cranking will be around 0v
if the cable is bad it will read voltage (even just 1 or 2 volts is bad and would indicate resistance in the cable where there should be none)

repeat this test for the negative cable (B- and the engine block or the metal housing of the starter)