Hello. I'm very new to rc boats. I currently have a turbo tech s600 racing boat. It goes about 20mph and lasts about 5-10 minutes. My battery is a two pin 1500 mAh 7.4 volt. I was wondering if I get a bigger battery with 7.4 volts and 5000 mAh, would it burn the motor up or would it run longer?

Run longer. Remember though, a higher capacity battery will be bigger and heavier. Make sure it will fit before you buy.