Hi, NiMh batteries are 1.2 volts each so you get packs of 6 to give 7.2 volts.

If you buy LiPo then these cells are 3.7 volts so 2 of them come together as a 7.4 volt, so very similar but the Lipo battery weighs less. Cells are individual units when you put 2 or more together they become a battery.

Each needs its own charger type, you want to buy an intelligent charger this will charge the battery and switch down to trickle when charging is complete.

If you check on the motor there will be a recommended voltage and current for the motor. The current used will be decided by the propellor and how big it is. Always check when the prop is in the water, i.e. when under load.

Specification for the MFA 800.

Approx motor diameter 50mm by 70mm long.

Operating Voltage 12 volts.

Current approx. 5.28A at max efficiency.

RPM at 12.0v - 4289 at max efficiency.

Weight 595g (approx) Shaft Diameter - 6.35mm (1/4")

If you fit a prop that on load is taking about 5 amps on 12 volts then it is running efficiently. However this is 60 watts quite a lot of power, so how much do you need?

You can buy batteries made up for 12 volts or LiPo 11.1 volts. without problem.

Going back over your previous threads you will go much faster and for longer at a cost!

An esc that can deliver 20 amps (gives you some leeway) and make sure it will work at the voltage you want, many just run on 7.2 volts.

I suggest you could have a good turn of speed from 40 watts power that is 12 volts at 3.5 amps or 7.2 volts at just over 5 amps.

The prop size will determine the current taken, so a bit of a balancing act. If you used 12 volts at 3.5 amps and use 5000Mah NiMi battery then you will get an hour plus run time.

Good luck

Roy