I haven't had much luck with the combined Speed Control / mixer board on my tank model.
It's running on a 9.6 volt Transmitter pack and powering some very small motors. Running fine until one of the components on the board went up in smoke and caught fire! It would have looked great in a boat without anyway to put out the resulting fire!
As it was only 6 feet away in the front room though I was able to extinguish the flames prior to it taking hold! Just as well this was only being used in a test chassis though.
Edit: I've taken a look at the board and it's working but I've lost Reverse on the right hand motor - Three of the Fets on the board have melted! I can't read what the numbers where on those either to replace as the others are varnished and very hard to read.