I've been struggling for some time with the thrusters causing the ESCs to reset. I've previously diagnosed this issue to various things, including poor power supply to the thrusters, a floating earth, a need for more decoupling on the controller board, and restricting the absolute power consumption of all the thrusters. But, while all these things have seemed to help a bit, nothing has made the issue go away completely.
While testing the new thruster design on my bench the other day using a simple servo tester, I was surprised to see I could still make the ESC reset even though everything was being run from a bench supply. This got me wondered - could the motors themselves be the problem? I chose cheap-o motors when I started out, partly because I knew they'd fail over time and so didn't want to spend a lot of money on them, and partly to see what I could get away with. Maybe I was being too cheap? So I've decided to upgrade the motors to something a little better.
I chose the NTM 28-30S 800kV (available from Hobby King for $10 or from Amazon if you want to spend twice the money but don't want to wait); more expensive but hardly bank breaking. These are very similar in size to the old motors, but I still needed to tweak the thruster housings a little to make them fit. One big plus was the ability to bolt the props onto the motor rather than relying on a friction fit.
The final thrusters look identical (unsurprisingly).
The bench tests looked promising so now I just need to buy a few more and test a set on the ROV.