Below is the spec for the Trunigy SK358-900 motor.  In the spec it read rated power 700w and, well that was not true for my motor.  I was running along at 45amp at 12.5v as measure by my power meter.  I never exceeded 650 watts, with the battery fresh at 14.8 volts and 45amps the maximum power 666watts.  I never allowed the system to go beyond that.  In the first test I did take the power to 50amps for a very short period of time to verify the ESC could handle it but the remainder of test 1 and all of test 2 was done at 45amps.  Before doing the 50amp test I waited until the voltage reading on the battery was down to around 12.8volts, this would have been in the range of 640 watts still well below 700watts.  

I was using a 3300 4s battery and a 50amp ESC with a 12x6EP APC prop.  The failure occured on the second 2.5 minute run. Somewhere near the 2 minute point the motor released lots of smoke and came to sudden stop.  

You might wonder why I am doing such a thing, I was testing ESCs for a friend and it was easy to use the motor on my Trophy Trainer.  I had the ESC running full bore, 2ms pulse from servo tester.  Maybe there is something I need to know about specs and how much you can trust them, but I got led astray by this one.  I just realized the spec say "Max" current 60 for the ESC but it never says what the max current or continues current is for the motor is, I wonder......  Oh well live and learn.
Andy

TURNIGY AerodriveXp SK Series
AerodriveXP SK Series motors are designed for those who want the very best in outrunner technology for their R/C plane. Typically an efficiency improvement of around 8-10% can be seen over similar classed motors. This is in part due to the following;
 
Stator Laminations: .2mm
Magnet Type: N45SH
Bearings: Dual oversize (Japanese)
 
 
Model: SK35-48 900
Kv: 900rpm/v
Turns: 4
Resistance: 35mohm
Idle Current: 2.9AShaft: 5mm
Weight: 171g
Rated Power: 770w
ESC: 60ACell count: 3~5 Lipoly
Suggested Prop: 11*8, 13*6
Power equivalent : .25~42+ glow engine

When buying a cheap motor or any motor for that matter, remember the 3 gram rule of thumb. watts = 3 X weight (in grams). It is especially useful with cheaper motors such as those HK sells. Thier specs are always overstated. I've used turnigy and others with good results, but I am careful starting off. I always test on the ground and in the air with an Eagle tree logger before pushing the motor to its max.

P.S. 171 gram = 513Watts

I was just over on the Go Brushless web site looking at Scorpion motors.  The specs for the Scorpion SII 3026-890 show Max Continuous Power 1025 Watts and a weight of only 205 grams.  Using the '3 gram rule' the maximum power would be only 615 Watts.  Would information from Scorpion be that far off base?

Dave,
I'm with John on this one: at 200 grams it is 600W motor with very, very, very brief 1000W spikes.
This is dreadful marketing practice.

Dean

Hi John,
One question.....where did you place the Eagle Tree temperature sensor for this test? I used mine quite a lot and I managed to stick the sensor inside the motor on the windings....carefully. The right place would be inside the metal core of the stator, but this is not the easiest thing to do.

I've found the E-Max/Arrowind motors to be great value for money. So far I have not had to change bearings but from this forum, it does not look like a big deal to do this. All of the .40 size profile stunters around here are using the 2820 with an APC 11 x 5,5 E prop, and the motor is almost cold when we land. The actual metal core is just warm but not hot. I managed to warm one up a bit more when I tested it with a 12 x 6 prop. Some of the Turnigy's also seem to be fine, but it seems like the SK series are not much good.

Lately, I have tested some of the newer E-Max GT-series motors, and I still prefer the standard versions. The GT's have the centrifugal fan at the back and prefer to be front-mounted. For the same size model, the older 2820 runs cooler if you get a decent airflow through it. Maybe after some more testing I may be more impressed by the GT version.

Keith R

Hi John,
Okay, you are pushing 1000W for maybe 25 seconds, and not stunting.
You'll probably get away with this for a long time, especially if the motor temps are within reason, like they are.
I think you suspected that already, though.
Dean

Kieth,
I stick the temperature sensor right up in the middle of the motor, basiclly as you describe. You are right it is not always easy but its the best place I have found so far.

I have had good luck with the Turnigy motors, I prefer the blue and red ones, but the one SK I have has performed very well

In scale I run the motors much more conservatively, but as I noted before they cost hardly more than low nitro fuel, so if they only last for enough flights to compare to using a gallon up I would be happy. In fact they seem to last a lot longer as long as you are not over prop'ed.
John

Andrew,
This is a very good motor, http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=8486 It looks like it would replace the SK and is in stock. I use it for Navy Carrier and it handles 600 watts  with 1100 watts bursts. The shaft can be reversed with a little work to accommodate  rear mounting.
John

Andy
Most motors can be reversed, but it is something to mess with, the Turnigy's are fairly easy to change.  Another line of motors I have had good luck with are the Exceed RC, this one is similar to the ones we have been talking about, and it does mount to a firewall. In fact I just bought one recently. I haven't used it yet but Motocalc simulations show it a bit better than the than the turnigy.
Trouble is hobbypartz does not always have them is stock, but they are usually restocked fairly quickly.
http://www.hobbypartz.com/monsterpower-32--770kv--outrunner-brushless-motor.html
John