keep frying motors

[toddilgen]

i bought hop up motors for my micro hydro's, a 3800kv, and a 4200kv. they are rated to 500 watts. i ran a 30mm x 1.4 prop and a 27mm x 1.4 prop. the 30mm burned up both motors after 1 run each. this is the prop that the manufacturer recommended. the 27mm would never hook up. the boat would hop badly and eventually one of the blades would snap. but with this prop the temps were where they should be. the stock motor was 2600kv, so these are a considerable jump in performance. and i am limited in prop selections due to the driveline. the boats i am running are the mini cat racing hydro's. they only offer 27mm, 30mm, 32mm, and 35mm props for these boats. i am running castle barracuda 80's in both boats. i switched the timing advance to the lowest setting on the castle esc. but i am scared to go run the new motors. please help?

[NorthernBoater]

How many cells are you running?

[toddilgen]

thunder power 11.1v 2070 extreme series

[kahnen]

I'm not an expert but seems like you need lower motor KV or lower you voltage. My understanding is for sport running you should have 20000-25000 rpms, racing is 25000-30000 rpms. With your setup you have 42180 rpms with the 3800 kv motor and 46620 rpms with the 4200kv motor.

[toddilgen]

so what's the problem with all those rpm's? that just means more speed right? and that's a good thing right?

[NorthernBoater]

Higher voltage and higher rpms means it will draw more amps.

[NorthernBoater]

Also as I understand castle does not recommend changing the timing advance from the defaults.

[toddilgen]

so what do you suggest? i bought these motors from the company that makes the boats i'm running them in. and they say they will work. the only difference is i am running a castle speed control instead of there's.

[NorthernBoater]

so what do you suggest? i bought these motors from the company that makes the boats i'm running them in. and they say they will work. the only difference is i am running a castle speed control instead of there's.

What voltage did they recommend running them at. I am not familiar with those motors, so I do not know the quality of them. But I would say, as a guess, the bearings are probably not rated past 35k RPMs.

[txboatpilot]

Drop down to 7.4 lipo instead of 11.1.....Your stock set up was designed to run at 11.1V x 2600Kv= 28860 RPM ..perfect for sport running...new motors have 3800Kv x 11.1V= 42180 RPM that is to mush rpm for these motor on your range of props...that is why the motors fry!!! drop to 7.4V x 3800Kv= 28120 RPM..that is right around factory rpm....4200KV x 7.4V = 31080 RPM..just a little faster than stock....All these setups with 7.4V will run faster because the batteries are lighter!! just try to keep it on the water, any time you lighten a boat it dances around more!!

[kal1b3r]

thats a really high rpm.
by the way, are you running two motors in your boat? im just asking, but if you are, and they are wired in parrallel and you hook up 11.1 v each motor will get 11.1 v. but if they are in series then you should have no problem because half voltage will go to one, and another half will go to another.
i used to think that more voltage was better for boats and that they would go really fast, but now its just a waste of money. lol.

[andym]

Mate they are right, way to high a kv. I don't know if they are running 380 size motors in these little rockets or not. If they are try a venom 3100 kv thats still way hot and I have run one on a acadamy outboard with a 33mm prop and it handled that well, your hydro has way less drag than this and it would go bloody quick on 3s. Keep on trying and when you have it sorted I might by one and copy your ideas that work. Cheers

[toddilgen]

these are mini cat racing hydro's and the motors are brushless 280 size in-runners.