Yes try taking the plugs out, at least to eliminate the possibility of water in the cylinders..
If that's good,
then get an inductive DC Amp tester, sears has them, and place over your positive cable to the starter and crank over, if it exceeds around 190 Amps, change the starter.
You may want to check for voltage drop to all points, neg. and pos test. cables, relays, etc.
Are you sure your batteries are up to snuff.?? how old are they? are they rated for the proper Cold Cranking Amps for your engine? or they may have just lost there cranking amp power.
You should of never of needed 2 batteries to crank your engine over from the start..