Ideal numbers on engine, kv, battery and prop

[Recty]

I'm having a little bit of a conundrum, hopefully someone has some good advice for me to help me solve this issue.

All numbers below are just examples, not the true numbers I'd be working with but they are ones that provide easy math...

Let's say I have two 3S 5000mAh batteries running in series, so running at 6S with 5000mAh. At 22.2v, it would spin my 1000kv motor at 22000 RPM.

Now if I have two 2S 5000mAh batteries running in series, so 4S at 5000mAh... and so it's 14.8v and I'm using a 1500kv motor... that would also spin at 22000 RPM.

So here's my question... is there any benefit to one setup over the other? This would be for a catamaran, like a 29" Miss Geico or one of the other similar bodies. But to me, that doesnt really matter... I'm just trying to find out if there are any advantages of going with 6S over the 4S? Will one run cooler? Will one need a bigger ESC? Would both draw the same amps to spin the prop at full speed? Something tells me that a 6S at 5000mAh is going to run longer than the 4S at 5000mAh, but I'm not sure why I think that.

Any advice you can give would be great, it will definitely help me in making my future purchases!

[siberianhusky]

If everything is the same but the kv and voltage the 6s setup will draw less amps.
W=VxA. So if both motors are doing the same amount work (watts) with more voltage the amperage has to be lower.
If you resist the urge to run a bigger prop because everything is running cool you can get away with a LV (low voltage 2-6s) esc, you decide to push the amperage limits at the max voltage you will probably shorten the life of the esc substantially.
Not all escs can handle 6s voltages so check the manual.

[Recty]

So really, I should try to go with a 6S setup if at all possible. It would be better to run 6S at 1500kv than to run 4S at 2250kv? Better as far as long lasting batteries (5000mAh battery going to be able to provide power for longer due to less amps being pulled) less heat due to less amps and the downside would be more weight, but in the boats I'll run its fine to have another half pound heavier for batteries, will just make it more steady if anything.

[Chilli]

Your ESC will run cooler on 6s but you will also pick up additional heat with longer run times. So you will still have to watch your prop selection and monitor temperatures. Weight is really not an issue with the power we have today...as long as you put it in the right place so you have the proper CG.

[BHChieftain]

While the higher voltage configs can run cooler, note that for boats in the 30" range, a very typical config is 4S setup with a 1800-2200kv motor range. I have personally standardized all of my boats to run on multiples of 2S1P 5000 mah packs-- so I can run 4S1P or 4S2P. Packs are cheaper than 6S packs that way. The 4S2P will give very long runtimes and also runs cooler than 4S1P. But say you also fly helicopters that call for 6S packs-- then configuring your boat for 6S makes sense. So you have a lot of options.

If you are planning on running in any NAMBA events, there are restrictions of what type of motors and power to use in some classes. Below is the NAMBA rulebook as FYI.

http://www.namba.com/content/library/rules/namba_rulebook.pdf

Chief