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Twin Brushless Motors at full power but boat hardly moves

Old 09-13-2020, 07:28 PM
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Chrisrox36
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Default Twin Brushless Motors at full power but boat hardly moves

Hi! I have just set up a twin 40a mystery ESC and twin racestar 4800kv brushless motors with 2 three blade rounded props spinning CCW. Took it on a test run and it was at full throttle spinning so fast but the boat hardly moved. What am I doing wrong? Any help is greatly appreciated. Thank you.

I am new to all this since my 2 little boys have started to become interested in modifying cheap boats so they go “faster”...
Old 09-14-2020, 05:22 AM
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You haven’t given us nearly enough information to help you.

- exactly what boat and size?
- what voltage?
- what size props?
- what size motors?
- surface drive or submerged drive?
- a few pics would help...

Based on the limited information my first guess is the wrong props spinning too fast, but that’s just a guess. Answer the above and we may be able to get you moving.



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Old 09-14-2020, 08:32 AM
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Default More info for you. Thank you

Unfortunately, it is not allowing me to upload pics yet, but here is a little more info.

The boat is a Syma Century

my transmitter is an Austar AX5S 3 channel

the motors are racestar 2435 4800kv brushless

the props are 3 blade rounded and just about 30mm diameter.

I believe it is surface drive. The shafts come out at the back of the boat on both sides of the rudder.
Old 09-14-2020, 07:11 PM
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What voltage are you running?





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Old 09-14-2020, 08:04 PM
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Default 2s lipo

What voltage are you running?


I am running 2s lipo 7.4 volt battery



Old 09-15-2020, 06:15 AM
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Without actually seeing your setup, you seem to have two issues. One, the motors have excessive rpm which causes the props to cavitate (slip and draw in air). Too, the props are slow speed designs and cannot handle the high rpm positioned close to the water surface. You could try more appropriate aftermarket props but they may overload the motors.

While this is an over-simplistic example, most high speed props have pointed tips and blades shaped to bite the water. All I know about your model is from a couple pictures online, but the stock props look “better” than any rounded designs. Can you try those? If you do, only run for 60 seconds and bring the boat back in to check for excess heat on the motors and ESCs.


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Old 09-15-2020, 07:37 AM
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Thank you so much. Your knowledge is much appreciated!

i do have extra props from a Feliun FT011 that I can try on there and they are the “blade” style that you say. I’ll let you know what happens. Only 6 more posts and then I can start posting pics.

Thanks for helping me get back on the water!
Old 09-16-2020, 06:43 AM
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No need to wait for more relevant posts here. Just go to the “test posting forum” and make four posts with the title and content as “test”. Takes two minutes tops, then you can post pics.

https://www.rcuniverse.com/forum/test-posting-forum-72/



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Old 09-16-2020, 08:12 AM
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thanks for getting me going with pics.. now I can show you..






per your suggestion, I put these 2 blade ones on and will test out hopefully today


Old 09-16-2020, 03:11 PM
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Yep, definitely surface drives. Those props will work better, the rpm is still pretty high so don’t try full throttle from a dead stop just yet, half throttle should work. As you get used to it you’ll find the best technique. Fingers crossed.....





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