Overheating on 4s?!?

[Nutbar]

Ok, something is definitely wrong here, at least, I think. I'm running a bone stock Castle Spartan w/dual pickup rudder, and aluminum cooling jacket. I took my sexy new pair of 2s 12,800mah 40c lipos for a test run, and everything was going very well for about 10-15mins, but then I thermal. She was smooth, stable, going about 35mph, running WoT almost the whole time. I had a couple of spin outs, but that's it. Water was smooth. The cooling lines were open and flowing. I had a little more than a 1/8" gap between the strut and dog.

I had just regreased the shaft and lubed the motor/strut prior to this run. I always place my batteries all of the way up front for maximum stability. I brought her in after the thermal, and everything was pretty hot. No smoke/fire, but warm. The motor was hot, ESC was hot, lipos were both warm, wires were warm, Traxxas connectors were hot. The wires and connectors got so hot that they started to melt thru my swim noodles! Lol! So, what the heck?

1. I shouldn't be overheating on 4s on my setup, right?

2. I think my flex shaft might be rapidly losing grease because I notice it's pretty dry after each run. I think that might be causing the overheat? Should I try removing the teflon liner?

3. What's the best way to keep grease on the shaft?

4. The overheating is probably not due to my larger than average batteries/run times or my full forward battery placement, correct?

5. Would a wire drive run cooler? Can you be hard on the throttle with wire drives and not worry about breaking them?

Thx in advance for all responses!

[Diesel6401]

No it shouldn't be. Could be binding in the shaft. Not keeping grease could be an issue. Maintain wot as much as possible, less then full actually causes higher amp spikes. Runtime is ridiculously high for a boat. 10-15ms at less than full throttle I'm surprised something hasn't blown yet
Cut the rundown down to around 4-5 min or so. Keep on the throttle as much as possible. Make sure you have a gap better the strut and drive dog.

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[tlandauer]

10-15 min. of running is way too long. You are lucky that your batteries did not puff. Time your run and never exceed 4 min. Infact when you are testing temp. , bring her in under 2 min.
You flex will look dry after this long of a run. If you don't have water coming thru your stuffing tube, you should be fine. I use a grease pump to make sure the grease gets in all the way . Proboat sells it.
If the boat is running too wet ( forward batt. placement) , you will pull more amp draw and generate more heat. But your over heating is because of extreme long run time.
Can't say anything about wire drive, never had experience on that, sorry.

[dag-nabit]

I agree that the 10-15 minute run times are too long, and may the prime source of your overheating on 4s

A few things you could look at:
1. Length of wiring between batteries and esc, and between esc and motor. Wiring runs should be kept as short as reasonably possible.
2. Are you still running the x640 prop? It is smaller diameter but higher pitch than the stock 42x59. The smaller diameter should compensate a bit for the higher pitch, but your prop may be adding extra load. It really shouldn't be an issue on 4s, but could be "the straw" on 6s.
3. Prior damage to components.
4. Strut angle, should be negative, or at most 1-2mm positive or negative trim. Too much strut angle can cause binding.
5. Try running batteries further back on 4s, this will lift the bow and reduce drag on the hull. On 4s stability should be less of an issue than when running 6 s.

The Spartan has a tendency to "auger " grease out the back of the stuffing tube. Adding a grommet or piece of rubber hose between the hull and strut can help. Or you can modify the stuffing tube like I did, making it longer and fitting it into the end of the strut. After modifying, I have good grease residual on the flex/wire drive after two back to back runs. (4-6 minutes each). Another benefit to this mod is it helps keep the strut from getting bumped out of alignment. It is a bit more fussing getting the initial alignment set.

Because the wire drive has no wind to it, it is less apt to auger the grease out of the stuffing tube.

I run a .187 cable in one spartan, a .078 wire in the other, both have proven reliable. I have a very slight preference for the wire drive. There is no specific reason why, just do.

Kevin