Electric vs mech water pump

There is an ET benefit if AND ONLY IF you shut off your alternator during the pass. Otherwise you are just transferring the water pumping load to the alternator. If you are even thinking about running on the street, IMHO you could better spend your money elsewhere. Also, since you have moved the battery as far as possible from the alternator, increasing electrical loads seems kinda silly. Big fat battery cables can help prevent some voltage drop, but they are heavy.