My YEP HV 120A died within minutes without water cooling some years ago. The problem with water cooling YEP is that there is a junction to battery minus. If you get a second leakage at the motor you can have the full voltage through the water and you feel it very bad when you are swimming besides your board. So i made a closed loop water cooling with some hoses wrapped around the battery box. This helped.
Also have a close look on the wires soldering, one motor lead disconnected after short time of use.