Hor rocket

[Yaky]

I have a 3900KV motor with a 120 amp esc,is a 11.1 v battery as high as i can go?

[tiqueman]

That's actually over what you probably should be unless your doing strictly SAW passes on a quality motor. So in answer to your question, yes. 3S is your max voltage.
A lot of stock boats, proboat etc are in the 22000 to 30000 rpm range. Your set up is currently over 43000 rpm unloaded.

[Yaky]

Thanks for your quick reply i'm new to boats.

[tiqueman]

No problem. Welcome to the forums.

[Yaky]

What does SAW stand for please.What battery set up would you advise.

[tiqueman]

Sorry. I should have explained. Same question I asked way back when. SAW stands for straight-a-way. Typically just a very short run containing a couple passes to achieve the highest speed. SAW setups generally wont run long because of the heat, amp load etc that's being created. Too long a run and

It seems like you may be most economical using a 2S set up. 7.4 volts will give you about 28k unloaded rpm (voltage x KV) 3S would basically be your SAW pass battery. Also a general rule that's good to follow, every time you voltage up, you should prop down. You can always work back up if you find it can manage the heat and amperage.

[martin]

Straight A Way, boats run in straight bursts for maximum speeds. Usually pushing things to the limit with set up hence the short run times.

[siberianhusky]

Have a similar kv Lehner motor I ran in a 26" cat using a pair of 2s 5000mah packs in parralal, pretty sure it wouldn't have lasted long running 3s, amp draw was high enough as it was, would have had to prop way down.
Lehner is a high quality very efficient German motor, not sure how much luck I would have had with a lower quality motor, ran some serious amps through that thing! Was probably the fastest boat I've owned, can't afford to keep running boats that fast, as they say speed costs, how fast do you want to spend!
Of course you don't HAVE to see how fast you can make it go.......was the main goal of that project though.
Personally think an Aquacraft UL-1 motor running 4s with a T-120 esc is the natural setup for that hull you have, much lower amp draw running 4s, easier on the equipment. I have the 29" version of your boat, good hulls!

[Yaky]

Your advice re batteries sounds just right and understandable for my project (a chance to learn throttle and steering control) and a few short bursts to get a top speed readings. I've just got a watt meter and temperiture guage + extra props, so will try your advice noting readings and speeds on a gps. I'm away now for a holiday will let you know results when back and boat is finished. Hopefully no bonfires. thanks again.

[Yaky]

Thanks for your reply, short burst keep things cool, thats good advice.

[Yaky]

I've looked at Lehner motors and mine is not one, no name caution needed! My project is also top speed and after ive tried present motor props etc,will look into your Aquacraft set up advice for this hull, thanks for your advice. Being new to this hobby it all helps.