Thanks Pred (Uncle G), it is already a brushless system and I installed a 120A ESC. It has only had one run which you have seen and the seawater inside would have kept everything cool. I was only running on 2S and when I got it out of water all I was more worried about was getting the water out of the hull not checking temperatures. For realistic running 2S is ample and even with that 1/2 to 3/4 throttle would be all that is required and I dont think over heating on that would be a problem. But I have seen this running up to 6S so water cooling will be needed if I ever try going up the cell range. For the moment I just need to do some maintenance and sort the electronics so it can be relaunched without having to rush things like its initial run. The lake where I have sailed is small and has ducks and fish so not really suitable for anything but low speed electric.