tiny trolling motor for kayak/canoe fishing

Discussion in 'Propulsion' started by srimes, Oct 1, 2008.

  1. srimes
    Joined: Sep 2008
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    Location: Oregon

    srimes Senior Member

    I've used a 34 lb thrust trolling motor on a plywood canoe, and while it's good at moving the boat it's very heavy and overkill for using it like a trolling motor on a full sized fishing boat. The motor weighs, what, 40 lb? That and 60-80 lb for the battery makes it so the canoe is less practical to use than a jon boat and trailer.

    I'd like one sized for a kayak that would be good for for positioning the boat while fishing. Max thrust would be no more than the minimum thrust on the 34 lb motor. I don't know how much this is, but I would guess that 5-10 lb max would be plenty.

    Any ideas on making one of these cheaply? Are any R/C boat motors submersible?
  2. Guest625101138

    Guest625101138 Previous Member

    There are some really nice RC motors, controllers and batteries around these days. None are waterproof to my knowledge but that does not present a particular challenge. (Only A123 lithium batteries have shown reasonable water safety to my knowledge - other makes would need waterproof housing)

    This place is the best value I have found:
    A motor rated around 100W would do something useful.

    I have used scooter parts on a boat with success:
    You can see the current required to do different speeds indicated on the GPS. There are two 12V batteries in series so about 200W for 9kph on the cat. A good canoe would be driven more easily.

    An alternative is to go for a pedal powered boat that leaves the hands free. The latest version of my drive module weighs less than 10lb including the seat. It leaves hands free for fishing or myriad of other things.

    You could also look at a Hobie Mirage or Wavewalker if you are not inclined to build a drive frame.

    Of course pedal power helps build the appetite so encourages more focused fishing. If the fish don't bite then you at least get some exercise.

    Rick W
  3. srimes
    Joined: Sep 2008
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    Location: Oregon

    srimes Senior Member

    Thanks Rick, but I'm not looking for this to be the main source of propulsion, just positioning the boat and moving slowly while fishing along the shore 2-3 mph would be plenty fast. Static thrust to fight the wind is more important than speed.

    I figure the simplest would be a motor that could be submerged like a regular trolling motor. If it can't it'll need to be built like an outboard to keep the motor dry. The battery would be in the boat so I'm not worried about that.

    Could I take a motor and dip it in epoxy to waterproof it?
  4. Guest625101138

    Guest625101138 Previous Member

    Minn Kota make a range of units:
    I have not found weights but the Endura is not a particularly large motor.

    You can save weight on the battery if you go for a lithium battery. This one will give you useful operation:
    It has ample power rating. Energy is a bit limited so you might want maybe one for each hour of usage at low speed. You can see they are expensive but they weigh around 1lb. This is where you can really save weight. This battery is able to pump out 150A so about 5 times more then the Endura is rated at.

    The one precaution is that the battery will not like getting wet. Lithium and water are an explosive combination so if the water can get into the cells it could be nasty. A123 batteries are more expensive but do not explode. People are buying Dewalt battery packs to get the cells because they use A123 cells.

    Fiddling around trying to waterproof motors when you can get something like the Endura would simply be a waste of effort and money. If weight is the issue and expense no concern then buy the lithium batteries. Four of them will give you useful range.

  5. BHOFM
    Joined: Jun 2008
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    Location: usa

    BHOFM Senior Member

    The Endura 30 weighs in at 21lbs. 30lbs thrust for 14'

    From $109 to $121
  6. srimes
    Joined: Sep 2008
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    Location: Oregon

    srimes Senior Member

    I have an endura now, and it's a good motor. It's just way more power and weight than I need.

    That battery looks cool though. Unfortunatly, money is an object, but I have been thinking about using lithium batteries. But I want to try out the motor first so that I can see how much energy it uses.

    Maybe an RC motor and flex shaft to turn 90 deg. Any idea what the minimum bend radius is on those?
  7. BHOFM
    Joined: Jun 2008
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    Location: usa

    BHOFM Senior Member


    I have messed with RC boats for a long time, and even
    the hottest motors won't produce enough to move even
    a small boat. The least bit of wind and you would be
    going the wrong way. They are made to turn very high
    RPM to keep them cool. They are short lived under heavy
  8. Guest625101138

    Guest625101138 Previous Member

    The motor in the Torqueedo is one of the high performance brushless motors. It weighs about 1lb. The whole unit included lithium battery weighs 11kg:

    The new brushless RC motors have huge power to weight. The thrust for power relates to prop diameter but it will waste a lot of power if spun to motor rpm. Therefore you need to gear it to get best results with a small motor. You could use a larger motor and run it slow instead of gearing. Something like this would have the grunt for direct drive:
    The 11V battery would be sufficient. And a controller like this should be OK:

    A length of machinable aluminium or high strength stainless will make a workable curved shaft.

    You need the lowest pitch, largest diameter prop you can get hold of. This 8X4 is a reasonable place to start:
    Maybe this one a bit stronger:
    You can see the prices are mind boggling.

    The attached photo shows a spring steel curved shaft on one of my early drive frames. You would mount the motor just forward of the midship and bring the shaft down the side of the hull so the prop is just behind the seating position. Shaft would be about 4ft long. The offset thrust will need slight rudder to counter. Go easy on the revs because the prop could break.

    If you can set this up it will provide a reasonably efficient system. I have done some rough estimates on the hull drag at 7kph for a typical canoe and attached the prop analysis for the bigger prop and a 10X8. The latter is more efficient but the motor revs are lower so might be harder to control. It should take about 5A at 11V to do 7kph speed so battery life around 1 hour with the 6Ah battery.

    You can get cheap metal props that are used for stirrers from McMaster that would be stronger but a 10X8 model plane prop is certainly worth a try. The forces are not very large.

    Rick W

    Attached Files:

  9. Guest625101138

    Guest625101138 Previous Member

    You have not messed with the latest stuff coming out of China then (or cz). This stuff will get a small person into the air. Massive power to weight. This one is good for 6kW on 37V:
    Not bad for a motor weighing 1.5kg. If you shop around you can get ones good for even higher power.

    They are also efficient as well even when running at high power. They are intended for short duration so have to be derated for continuous use but are certainly capable of over 1kW sustained if properly cooled.

  10. Guest625101138

    Guest625101138 Previous Member

    Here is a bigger one rated at 6.5kW peak:
    These things have impressive performance. The controllers are even more impressive. Lithium batteries are viable and on the verge of being safe for use around water.

    I expect we will see a lot more of this stuff coming out with lithium batteries in the next few years that will kill small ICE outboards in price and performance.

    Rick W
  11. harlemriverman
    Joined: Oct 2005
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    Location: New England

    harlemriverman Senior Member

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    FAST FRED Senior Member

    Recently at an antique shoe I saw a really early electric trolling motor.

    It WAS a 1/4 hp 12V DC huge (like a refrigeration motor) unit hooked to a flex shaft.

    So a hobby shop motor should have no problem , IF you can find OTS parts .

  13. cahudson42
    Joined: Dec 2007
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    Location: Orlando, FL

    cahudson42 Junior Member

    To perhaps beat a dead horse, if you take the $109 Endura 34 and eliminate the use of the 'speed coil' resistance banks by using a 24V scooter PWM (will work without overheating in your case because of the low thrust/current required for trolling) you will also be able to use 2 small scooter batteries. Total weight may then be OK?

    I used a setup like this with the Endura 34 all this last summer on a 12' Jon boat. Trolling at 1.4 - 1.6 mph, current to the motor was about 10A at far less than 12V - can't quite remember - might have been about 8V. Works out to less than 5A to each battery - perhaps more like 3A -4A. And the Bass fishing was really good because we were so quiet, and could precisely control our speed. (At 1.6, it seemed we would get strikes - but hook them less. At 1.4, hooked strikes seemed definitely higher - this on Lake George, NY)

    You would be able to use 2 very small 12V batteries and have plenty of trolling time..

    I do bring oars however..

    If the weight is still to much for you, since you are running way below the 34lb Endura rating, you might be able to turn down the motor body exterior. I have not dissembled an Endura yet (will do so as soon as one fails) but if the skeg is solid, it might be sawed off. Then the cylindrical apparently-cast body turned down somewhat on a metal-cutting lathe. Worth the trouble? Don't think so - for me at least.

    You may have seen it, but if not there is some info on using a scooter PWM with the Endura at: http://www.cfnet.net/tm
    Last edited: Nov 15, 2008

  14. sparky_wap
    Joined: Mar 2008
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    Location: Suffolk, VA USA

    sparky_wap Junior Member

    An easy solution about 25lbs.

    Take a look on EBAY for small trolling motors. There are some in the range of 12 to 26 lbs thrust. One is listed right now with 12 lbs of thrust and weighs 8lbs. Buy a small (12v 25 AH) AGM battery at about 18 lbs and your total solution will weigh 25 lbs.

    If you wanted to spend a little more, you could buy (2) smaller 12 volt batteries and a scooter motor controller + throttle (about $35 at TNC scooters) and get variable speed at about the same weight.

    Sometimes you can find scooter batteries on EBAY very cheap. To save more weight, there are LiFePo4 batteries for about $200 that would work but would only save about 10 lbs.
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