I have just purchased a really dinky little wattmeter. It plugs in between your battery and your ESC (or whatever) and measures the WATTS..peak watts…voltage and current and peak current (rotatable, by pushing a tiny switch/button..one measurement at a time).
It was £10, and handles up to 30A and 30V.
So easy, no faffing about with wires and mini croc-clips..no accidentally shorting wires out…and of course if you are eagle eyed you can fit it in the boat and see what amps you are pulling as the boat zooms past! Not really of course, but there is a peak amp/watt memory on the thing for checking afterwards.
Get one. So easy.
Ashley