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Old Jul 21, 2014, 05:15 PM
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Joined Feb 2014
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problems with over heating

Just finished my Dumas kit 1241, 40" Chris Craft mahogany boat.
It is powered by a Graupner 600, 7.2 volt motor and an electronic marine speed controller. The kit doesn't allow for air or water cooling in the build.
First day out, boat ran great until the motor burned out. It was very hot to touch.
My other boat is 18 years old, a Dumas Chris Craft Cobra. The old motor was a bit slow so I installed the same Graupner motor. While it did get hot, it hasn't yet burned.
Anyone have any suggestion?
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Old Jul 21, 2014, 08:17 PM
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circuitfxr's Avatar
United States, FL, Wildwood
Joined Jul 2005
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Sounds like you need to install a water cooling system. There are many different systems available. You will need a pickup tube, some silicon tubing. and a cooling coil for around the motor. A small water exhaust tube would be helpful too. these systems are not expensive, but require some work to install.
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Old Jul 21, 2014, 08:19 PM
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Joined Oct 2011
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Quote:
Originally Posted by Ron been View Post
Just finished my Dumas kit 1241, 40" Chris Craft mahogany boat.
It is powered by a Graupner 600, 7.2 volt motor and an electronic marine speed controller. The kit doesn't allow for air or water cooling in the build.
First day out, boat ran great until the motor burned out. It was very hot to touch.
My other boat is 18 years old, a Dumas Chris Craft Cobra. The old motor was a bit slow so I installed the same Graupner motor. While it did get hot, it hasn't yet burned.
Anyone have any suggestion?
To much boat for a small motor?
To much prop for a big boat and small motor?

Probably all of the above.
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Old Jul 21, 2014, 08:38 PM
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bellingham, wa
Joined May 2006
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also how freely dose the shaft spin. Prop size and motor size all matter.
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Old Yesterday, 05:16 AM
Boaters are nice people.
Sneek, Netherlands.
Joined May 2004
4,790 Posts
Quote:
Originally Posted by Ron been View Post
The kit doesn't allow for air or water cooling in the build.
Hi Ron,

A 600 motor for a 40" hull is very optimistic, if you expect the boat to get (and stay) on the plane for a longer period of time.

I'd go with a 700 motor on 4S (provided the 700 motor turns about 1300 - 1600 rpm/Volt).

A 700 motor also should be watercooled, preferably can- and brushtab cooling, like the 700BB 9,6V Neodym in the picture:



Inlet, if possible, behind the prop.
Some picturs of your build would be nice to be able to tell what will work best.

Regards, Jan.
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Old Yesterday, 06:49 AM
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Joined Dec 2004
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There is one universal answer which applies to the problem of a motor over heating or burning up, TOO MUCH PROP!!!!

Any motor will work in any boat, providing that the load (propeller) is the right size to allow the motor to come to its normal operating RPM’s.

I can state for sure that a motor which can turn a propeller under a static load (in a test tank), will NEVER BURN UP WHEN IN OPERATION IN A BOAT, NO MATTER THE SIZE, as long as you use the same propeller that was used in the static test.
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Old Yesterday, 02:14 PM
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The prop is the one that came with the kit, a 3 blade prop. The boat is not designed to plane. The Dumas kit doesn't talk about cooling although it makes sense. Not quite sure how to design the thru hull water pick-up but the photo of the 700 motor does let me see how to design the cooling coil.
The kit does talk about the Dumas 2025 motor. Does anyone have any experiebce with it?
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Old Today, 05:31 AM
Boaters are nice people.
Sneek, Netherlands.
Joined May 2004
4,790 Posts
Hi Ron,

Check out the pictures in my MAS build thread to see how I go about installing in-and outlet for watercooling:
http://www.rcgroups.com/forums/showthread.php?t=1551192

Regards, Jan.
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