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Old Dec 01, 2010, 12:30 AM
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New Westminster, B.C., Canada
Joined Apr 2010
76 Posts
Question
Brushless conversion for a Jet Ski

Hi!

Now days, my little daughter really enjoys rc stuff, I am very happy with sharing my hobby with my little daughter!

Now she wants more speed for her toys, so that now I am in the process of brushless conversions for her rc cars and boats.

I am going to do a BL conversion for ABC Hobyy Jet Ski. Here is the web-site.
http://www.horizonhobby.com/Products...901#quickSpecs

I want a little more speed for this Jet Ski, since for the safety issue for my little daughter, I don't want super fast speed, and also I think this jet ski cannot handle much more speed.

Is this BL motor ok for this jet ski? Here is it.
http://www.hobbypartz.com/88e-ads-30...ool-motor.html

If this motor is a proper one ( I am not so sure whether this is too small for this Jet Ski or no.) do you think approximately how may percent of more speed does this motor give with a 2-cell Li-Po 5000 mAh battery?

And is a 35 A ESC good eoungh for this motor or should it be higher 35 A?

Your kind advices will be greatly appreciated! Thank you!
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Last edited by James K.G.; Dec 01, 2010 at 12:56 AM.
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Old Dec 01, 2010, 07:19 AM
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wparsons's Avatar
Canada, ON, Whitby
Joined Aug 2008
8,901 Posts
I would go for a bigger motor, I believe the jet pump in that boat is 22mm. I'm running a 28mm outrunner in my jet sprint knock off (tear into) and it only has a 19mm impeller.

On 2s, you'll want a motor in the 3300-3600kv range.

I run a 35A esc in my smaller drive, so I would suggest at least 50A for this.
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Old Dec 01, 2010, 07:26 AM
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Canada, ON, Rockland
Joined Aug 2008
24,077 Posts
If you want more speed considering this jet ski can use 7.2v or 8.4 volt (6 or 7 NIxx pack) Have you tried it with the 8.4v battery????

3000kv outrunner mite be hard to mount in the jetski depending on the existing motor mount and 3000kv seems very high for boating but not sure about jet drive..
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Old Dec 01, 2010, 11:20 AM
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Canada, ON, Whitby
Joined Aug 2008
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3000kv isn't very high at all for 2s usage, that's only 25k unloaded on a REALLY fresh pack (8.4v).

You generally want to aim for about 25k rpm loaded as the maximum for a jet drive so it doesn't cavitate.

I would suggest a 380s or 380L motor, with about 3500kv.

Not sure what your budget is, but here's what Feigao has in that range:
http://www.offshoreelectrics.com/pro...ushless+Motors

If you wanted to run 3s, this would work well:
http://www.hobbyking.com/hobbyking/s...idProduct=4947
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Old Dec 01, 2010, 03:14 PM
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Little Rock Regional, Arkansas, United States
Joined Sep 2002
4,586 Posts
Jetski

Here is my brushless jetski I did this summer. A CEN Wave Shark . A bit much for a younger driver but loads of fun.
Thread here:
http://www.rcgroups.com/forums/showthread.php?t=1298407

Video on post #12.

Stringfly <>++++
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Last edited by STRINGFLY; Dec 01, 2010 at 03:59 PM.
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Old Dec 01, 2010, 11:03 PM
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New Westminster, B.C., Canada
Joined Apr 2010
76 Posts
Hi, Everyone!

Thank you for your responses!

CEN racing jet ski is different from ABC Hobby Jet Ski, since Cen is prop drive, and ABC Jet Ski has an impeller jet drive system. So I think if putting a quite powerful motor, it will badly cavitate.

I think increasing speed upto 60%-80% would be ideal. But it is my guess!

My duaghter and I tried a 8-cell Ni-Mh battery, and I guess it increased speed about 10-20% more, but that stupid 8-cell Ni-Mh didn't last long, and it became a garbage. So my daughter and I prefer 2-cell Li-Po 5000mAh. I think 3-cell Li-Po would cause cavitation.

Any good BL motor for 2-cell li-po 5000mAh battery to increase speed to the maximum without causing cavitation? If the motor shaft is 3.0mm, it will fit to the connector.

I don't know almost nothing about electric stuff, so your advices will be greatly appreciated! Thank you again!
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Old Dec 02, 2010, 07:37 AM
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Canada, ON, Whitby
Joined Aug 2008
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It isn't power that will cause cavitation, it's too many rpm's. If you keep the rpm at the impeller around 25000 rpm you'll be fine.

A feigao (link in my previous post) 380s or 380L should give you enough torque to spin the impeller, and with a kv in the 3500 range you'll be in the right rpm range on 2s.
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