Ok I 'm almost ready to test the boat with the BL motor but need to find out what is too hot for it? I have a water jacket on it to help and have heard they can take more heat than a brushed motor but don't know how much. Any ideas?

Well, sorry to throw this in, but, it depends. (I'll explain everything) Generally, brushless motors cannot take more heat than a brushed because the magnets loose their magnetism at a much lower temperature, i.e. Neodymium. Ferrite motors are a little less picky (but they always seem to die from overheating.... , and Cobalt magnets don't really seem to care how much heat they get (under practical conditions). I haven't seen a case where they we're killed from overheating, but I'm sure it's happened. Overheating for a cobalt is where the motor gets so hot the solder holding connections melt. I've had one get so hot the covering melted on my flying wing, but it still runs fine. Brushless motors are more efficient, so there's less heat to release.

Rules of thumb:
-The brushless should generally be much cooler than a brushed motor, unless you're drawing HUGE amps for long periods of time
-Too hot is where you can't hold your finger on it for 5 seconds without pulling away due to discomfort.

Exceptions:
Say you have a cobalt brushless motor.... it can probably run at a temperature that is uncomfortable to touch. If it leaves a burn mark, yah, it's too hot! [X(]

Where you going to run it in Eureka? Used to live there... [8D]

So, why hasn't anyone just made a brushless motor that just has it's sides just completely exposed to the water? No need for a water jacket, and I imagine the super-fast boats would benefit from it.

Hi e-sailpilot86. Thanks for the info. I guess I'll just have to keep checking it to make sure it's not too hot and see how long I can run before it does heat up. I was getting a full run after making a brass water jacket and brush coolers so hopefully it will be the same. Some times I run at the Adornie Center. They put in a really nice floating (cement) dock. If there is too much sea weed then I go to the bridge at Manila by the lumber mill and some times at the river mouth at Moonstone beach. The motor is a Feigao 8L in a 20" vee hull

Keep it under 150 and you should be ok.

Thanks guys. I could have sworn I read some where you could saftly run a BL motor up to 200 C. Glad I didn't do that.