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Aircraft Brushless Motors For Boats

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Old 03-07-2018, 04:44 PM
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All Day Dan
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Default Aircraft Brushless Motors For Boats

Can aircraft brush-less motors be used in scale boats. I need one with a KV rating around 800. Dan.
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Old 03-08-2018, 02:17 AM
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If you find a motor with the right spec, no problem. Apart from finding the right ESC. Boats tend to need different controls than aircraft, reverse being top of the list. In the real world, aircraft engines have been used to power boats plenty of times (e.g. Packard/RR Merlins in PT boats), but were usually derated so that they would last longer. The same considerations apply using an air motor in a boat - it is always working harder for longer and is not usually sitting in forced airflow, unless its an airboat.
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Old 03-08-2018, 06:58 AM
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Cooling could be an issue. Many electric motors for boats already have cooling built in. However, if you can add cooling to your aircraft motor there should be no problem.
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Old 03-08-2018, 07:01 PM
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A lot depends on the size and type. With that low Kv you will likely be limited to outrunner motors. No problem other than cooling which is a challenge with outrunners. I run outrunners in several race boats using a fan and sometimes a water cooled motor mount. If amp draw is kept low for the size (normal for scale models) then I don’t see why one can’t be used in a scale boat.

Kv is not the only motor spec to consider. Common OR diameters are 30, 36, 40 and 45 mm, lengths vary widely.. What size boat, voltage and prop will the OP be running?

There are many water cooled ESCs available, they need to be matched to voltage and maximum amp draw.


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Old 03-08-2018, 08:14 PM
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Thanks guys. All good replies. I need to replace the Astro Flight brushed motors with a kv rating of 800 with brush less motors. I can not find any marine motors with that kind of rating. It looks like I'll have to use the aircraft version with a muffin fan .Water cooling is not an option. Sterling 48
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Old 03-09-2018, 02:54 AM
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Cooling outrunners. You don't cool the bit that spins because that is just a magnet, you cool the bit that carries the coils, and this is essentially the flat mounting plate.
Inrunners and brushed can motors cool the static tubular part because that is what you can get at. The bits that generate the heat on these are deep inside, you can only catch and remove heat after it has traveled through the case. A short path with an inrunner, through the magnets with a brushed motor.
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Old 03-09-2018, 10:57 AM
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Thank you mfr. I never thought of it that way. Good input.
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Old 03-14-2018, 03:54 PM
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Originally Posted by mfr02 View Post
If you find a motor with the right spec, no problem. Apart from finding the right ESC. Boats tend to need different controls than aircraft, reverse being top of the list. In the real world, aircraft engines have been used to power boats plenty of times (e.g. Packard/RR Merlins in PT boats), but were usually derated so that they would last longer. The same considerations apply using an air motor in a boat - it is always working harder for longer and is not usually sitting in forced airflow, unless its an airboat.
Actually, the Packard engines used in the PTs were very different from the ones used in the Mustang. Here's what I found in a PT boat forum:
The Packard 4M-2500 engine was utilized in all U.S. Navy World War II PT boats. This engine was based on the 1925 Liberty aircraft engine which was earlier converted for marine use in racing boats. During the war the Packard engine went through various performance updates and modifications. With early engines rated at 1100 h.p. and progressing to 1500 h.p. during the war. The Packard 4M-2500 engine was a supercharged, water cooled, gasoline powered V-12 engine, weighing approximately 2900 pounds.

Your general comment is correct as the basis of the PT engine was the Packard Liberty engine which was manufactured for aircraft, notably the Curtis flying boats between the first and second world wars.

Last edited by Hydro Junkie; 03-14-2018 at 04:35 PM.
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