The SV 27 speed control is only rated at around 40 amps. It's easy to pull double this even in an SV-27. I've slowly moved up in speed controls for the P (4S lipo) spec classes to the UL-1 speed control then the Hobby King 120. The Castle ICE controllers are better still with data logging to let you know what current you are pulling. Along the way I've converted all the connectors to 5.5 mm bullets since overheating will melt the solder on the stock connectors.
When you overload electrical parts, the damage can be subtle. Insulation breaks down slowly from overheating. I've had several motors seem to run fine then not work after starting the next time. Motor shorts often take out the speed control. Controlling the current is key to power plant life. You can get an estimate from the run time and how much it takes to recharge the batteries. A data logger is eye opening when you see the current spikes as the prop enters the water. We get 150 amp spikes on P spec boats even though the average current is below 100 amps. Full P boats can get 300 amp spikes with averages around 200 amps.
This is all controlled by propeller selection. Unlike internal combustion power plants, electrics just keep producing more torque as the load increases until something melts. Modern batteries can easily supply well over 300 amps in a burst. The motors and speed controls are the weak link. We run Grim Racer 42x55 props on SV-27s, P spec tunnels, and UL-1s. I wouldn't go to a bigger diameter.
Lohring Miller
