Most newer fuel and water pumps will tolerate the 18 volts that a 16 v system will see when charging with an alternator .
What I have seen is cooling fans being damaged by the higher voltage.and also incandescent lighting on the car ....Also COPO Camaro's and DragPak smart window modules will not tolerate the higher voltage .
I use this voltage reducer that is made for electric golf carts to drop the voltage down to a usable 12-14 volts for radios and other accessories .
https://www.golfcartgarage.com/golf-...BoCLLMQAvD_BwE