To give you a meaningful answer, knowing the following will help.

Is this a fast / planeing model or a sedate one?

What size propellers are fitted / how many amps are being drawn?

How long do you want to run for?

Is weight or size an issue?

How many amps is the ESC rated at? Just to make sure it's OK for the set up.

I'm not being picky or difficult, but without knowing the above only vague answers are possible.

Chas.

Edit, I knew I would forget something important, the 600 motors have several variants, standard, eco, bb. Maybe others, which are they?

Edited By Charles Oates on 06/06/2018 22:43:13

Edited By Charles Oates on 06/06/2018 22:45:19

Peter. If you want to run them at 7.2V then the answer to "wot battery" has to be….the biggest capacity you can afford. 5000mAh ones.

A fire boat requiring two 600`s I feel sure will have the capability of carrying a fat Nimh battery pack easily.

Ashley