The "600" says that the can size is a bit shorter than 6cm. Commonly they used to be called "540" motors being 54mm long, but some manufacturers decided to "simplify" things by rounding up. To know what it is going to do requires that we know a bit more about what is going on inside it. There might be more information on the label.

You can make a boat run longer by fitting higher capacity batteries, but the downside is that they weigh more and will cause the boat to sit deeper in the water. Adding an extra cell or two in series to increase the voltage will make it go faster. There is the same consideration of extra weight, but add in the consideration that the motors and controls will need to be able to cope with the extra power.

Type of boat is important – a tug needs a different type of power than a race boat. Both can be fitted with some kind of 600 motor, but they both need very different ones.