Are you running 12 volts on the 6V starter? If so, the starter will draw more current than a 12V unit, but I think 500A would be a bit much. If you have access to a carbon pile battery load tester (not the 100 amp fixed-resistance "tester" a lot of parts stores use)you can find exactly what the current draw is. Check the battery terminal voltage while cranking the engine, then load the battery down to the same voltage and see what the current reading is. I've used that test for well over 50 years- - - -it works!
Jerry
