For those looking to calculated the approximate top speed of your board I’ve adapted an excel sheet that Vitalie created.
Download here: Electric Longboard Speed Calculator excel
Note: Going at 15mph or 24kph feels fast.
Basically when looking at motors you want something with a low KV (rpm= KV8 voltage). Also in the spreadsheet is gear ratio and wheel size.
Now this isn’t going to help you figure out what wattage motor you might need. Mine is a bit over 2000W and heaps of power.