on the SLOWEST setting, speed w/ troll?

-- Last Updated: Jun-01-14 7:21 PM EST --

Well, it seems that a trolling motor can get a canoe up to about 4 mph. but, this doesn't really concern me. At 4 mph, a 45 lb. thrust motor will be dead in an hour or so, provided 38 lbs worth of batteries are used. In other words, a 2 hour run would equal 100 lbs of equipment. To me, this isn't worth it.

I'm looking for a motor as a "paddle substitute". I don't need to be moving at 4 mph.

I'm wondering how fast I can travel before running out after about 8 hours with a 45 amp hour battery.

also, I wonder how long i can run at about 1.5 mph. thanks.

online data calculation

read thru:


The manufacturer of the equipment you’re looking at may have a graph you use to figure consumption at different aH loads/mph.

Helpful to learn tide speed rules:


and on your water, if there are reverse current eddies along shore.

A problem with electric motor systems is weight. Many paddlers figure that much weight moves a kayak into a not kayak vessel. Especially when out of juice going against the current the motor was meant to…

That will be tough to calculate

– Last Updated: Jun-01-14 11:04 PM EST –

I bet if you look around at data provided by motor manufacturers, you can find info describing how long a particular motor, when powered by a particular type of battery, will run at various power-output settings before the battery goes dead. However, you are asking what speed of travel a power output associated with a particular amount of battery life that translates to, and there just won't be a way to calculate that.

The problem is, a canoe with a light load only requires about 4 to 6 pounds of thrust to move along at a moderate speed, and though that info by itself is true, you won't find published data anywhere to tell you how fast a *particular* model of canoe, carrying a *particular* load, will go when powered by a motor delivering a particular amount of thrust, because surely no one has ever tried to catalog all the possible combinations (and the combinations possible out of that list don't even include consideration of the many dozens of different kinds of motors you can buy. The total number of combinations of battery-life/speed combinations for various canoes with just a few reference loads would be in the tens of thousands).

You are asking the impossible. I suggest you figure out the expected battery life at the motor's slowest setting (from manufacturer's published tables), and then just accept whatever speed happens to be provided by the motor's slowest setting when the motor is on your particular canoe. One thing you can be sure of, is that unless your canoe is loaded up like a container ship, the speed it travels at the motor's slowest setting will be faster than what that same motor would provide on larger fishing boats.

Modern motors are very frugal at low speeds. Gone are the days when motors provided low power by means of variable resistors. Nowadays, they "chop" the electric current into discrete fragments, and the smaller the fragments (shorter bursts of full-power application), the slower the motor runs. It's a very efficient method. With that in mind, make sure you know what speed-regulation method is used by any older motor that you plan to buy used. A person with your concern for battery life wouldn't want to get the old-fashioned kind of speed-adjusting mechanism.

By the way, 45 pounds of thrust will make your canoe go a lot faster than 4 mph, or at least it will be trying to go a lot faster (it might get bogged-down within its own waves (the hull-speed principle) and not go as fast as proportional calculations indicate that it "should"). No ordinary paddler can exert 45 pounds of thrust (measured at the paddle blade) for any extended time, but they can sure go faster than 4 mph.

Maybe consider gasoline instead
I don’t know what your reasons might be for wanting to push an electric motor to its maximum travel range, but I’m guessing that something is keeping you from simply paddling the boat. If you really need a motor, and that motor really needs to give you the ability to travel an extensive distance and return again, a small gasoline motor would be the ideal method. The initial investment will be a lot greater, but with about one-quarter the overall weight of an electric motor and its battery, you could actually travel for days, not just hours, and at a much faster speed too. Electric motors are great if you don’t have to go far, but poor if you do.

FISHING kayak forums
Sea Kayaker magazine reviewed a kayak system, I forgot the name. Search this forum’s search, there’s a prior discussion.

I have no expertise beyond the standard formula…for example, you need knowledge of prop design. Great. My head hurts.

But recommend:


None of that will answer the question

– Last Updated: Jun-03-14 9:57 AM EST –

As long as the question about battery life includes travel speed (whichever end of the calculation the speed value happens to be on - known or wished to be known), nothing you can calculate will answer the question for you unless you can find some published drag vs. speed values for the kind of canoe that will be used, and I don't believe that data exists for more than a handful of boat designs (such data HAS been published for a fairly large number of sea kayaks, but the question is about canoes, and MAYBE the data are out there). Mere mortals can't calculate how fast a particular boat carrying a particular load will travel in response to a given amount of thrust. Even hydrodynamics experts need to verify their calculations by observing the speed vs drag relationship in a test tank.

So, if the OP goes looking for a way to find his answer, he's going to have to expand his search parameters to include speed vs drag values for the particular kind of canoe he actually owns (good luck with that), or perhaps figure out an approximate answer based on speed vs drag values for a canoe that's similar to his own (still a long shot).

By the way, there's no need to do any calculations about propellers. All you need to know about the propeller is the thrust it produces at a particular power-output setting of the motor, and why would anyone want to calculate thrust when the data are already supplied by the motor manufacturer?

Of course, all talk of calculations is beyond what the OP was looking for. He was hoping someone had direct experience that might be of help, but it doesn't seem like anyone here would have such experience.

wide and deep
Quantifying the subject area takes great expertise but observational and subjective assessment of the important subject may be read or sorted thru in fishing kayak forums.

I do not know but expect, from a brief look at the available material there, commercial interests and misleading advertising is about. May Forums weed thru this for the poster’s benefit.

People spend a lot of money killing fish.

“Talk around” the point doesnt help.

– Last Updated: Jun-03-14 9:35 PM EST –

The point which should have been really clear by now is that no information about any particular motor or class of motors is going to tell the OP how fast his canoe will go, and none of that info will allow him to determine how long the battery will last at a particular speed of travel. No matter how much info he can find about trolling motors and battery drain, and no matter how long you keep talking about the nature of that information, his basic questions can't be answered until he knows the relationship between drag and speed for his canoe when it's carrying the proposed cargo weight. Until that info is found, and my bet is that it can't be found on the internet, he's stuck.

Of course, the speed/drag curve could be determined easily enough with reasonable accuracy in just a few minutes of on-the-water trials, using another boat (as a tow vessel), a rope, a spring scale, and a GPS. With the resulting data plotted on a curve, he could determine his boat's speed for any any trolling motor, running at any power setting, just by pointing at a spot on the graph (no math needed). Why? Because once at the boat is going at a steady speed, the values of thrust and drag are equal, and the thrust values have already been provided by the motor manufacturer. In addition, the battery-drain info supplied by the motor manufacturer would no longer be meaningless - it could now be used to answer one of the OP's main questions. Oh, and if these on-the-water trials are to be done, the tow boat needs to be powered, not paddled, so you can get a steady reading on the spring scale. It's such a simple solution to the problem that I should have thought of it sooner.

i have a 35 lb
Trolling motor with a 35 amp battery and a 120amp battery for my small sailboat. The motor has 5 speeds, I’m pretty sure that on the lowest 2 settings that thing would run for a long time on the 120 amp battery. Those settings would also probably move a canoe at 1.5. And the set up would be about 100lbs.

Seems this would be easy to figure with the operating amps divided into the amp hours.

Yeah, that gives you running time.

– Last Updated: Jun-03-14 9:58 PM EST –

However, even calculating the running time is sort of an approximation since the situation changes as the battery gets weaker (though the motor-maker's tables should account for that, at least for a particular battery). It is the questions having to do with speed that are currently not answer-able, and which are really the crux of the whole problem.

yes, GBG is correct but accuracy isn’t bringing the question, which the poster wants to do as a buy or project, into action.

Try this. Reviewing Sea Kayaker’s road tests, place the posters’s ( or ?) hull into a position on a slow/fast spectrum.

What is the differential between fast and slow hulss in that hull category and between fast and slow and the hull of interest overall ?

Not much as a number but as a number opposed to current flow, a significant number.

BUT ! this significant number is the number the electric motor system is designed to overcome or compensate with.

So of what speed range is this significant number and how does the amps/watts/aH figure into the equation ?

Still missing it

– Last Updated: Jun-04-14 12:34 AM EST –

I really struggled with the meaning of some of those "sentences" you wrote, but I think I got the gist of it. It's true that a lot of those kayaks have similar speeds at certain values of propulsive thrust, but that's because they are all sea kayaks, and the differences in dimensions, and the loads they carry, are not that great. But if the OP is wanting to calculate how far or fast he can go at a certain thrust value, he'll be off by a huge amount using those figures. We need to figure out the drag/speed curve for his CANOE.

So for one thing, you need to stop believing that the OP's boat is a kayak (every time you mention finding info for boats, you speak of kayaks). Canoes, big ones anyway, have more drag, and are slower. Even worse, odds are good that the mere fact that the OP wants to use a motor means his canoe is a big klutzy one that requires a lot of effort to paddle (it has a large amount of drag), which would be far slower than an ordinary canoe and therefore slower still in comparison to a sea kayak. How much slower? I don't know, but pretending it's just like those sea kayaks won't make the speed difference go away. And until someone comes up with a figure for the drag of this canoe at various speeds, none of us can know how much slower it will be. Further, a big klutzy canoe carrying a big load is slower than an empty one (even the motor and battery will weigh more than what someone on trip of several days is likely to carry, and anyone can tell you that such a tripping load slows you down), and we don't know what else the canoe will have on board. Maybe the passenger is a really big guy, or maybe there are two of them, and in that case the speed could easily be different by a factor of three or four, and that's hardly an accurate starting point. Don't believe me? Try solo-paddling a tandem canoe with a non-paddling partner on board, which slows you down enough if that person is small, but much worse if that person is big. Now add a load of gear and do the same. Your speed will be obviously slower than what it would be if paddling the same canoe with just yourself on board. So it should be clear that you can't ignore this stuff. A big CANOE does not have as little drag as a sea kayak, and if loaded, the difference rapidly becomes much greater.

Oh, and since you seem to believe that the motor will be a great equalizer among the different boats, you need to try to understand the relationship between thrust and drag (they are equal). For illustration, let's conservatively assume that a big loaded canoe has twice the drag as the sea kayaks you wish to use as reference values for speed and drag. Remember that the OP wants to know the performance at the lowest power setting, and with the drag difference of this example, at a given level of thrust, the resulting speed for the canoe would be half that of the kayak (that's a very rough approximation, since the relationship of speed and drag is not linear). Sure, if he's going too slow he can increase power, and then for a given speed, the drag of the canoe will be double so the required thrust will be double, leading to much faster battery drain. So the bottom line is the same as before: We just can't answer the OP's question until we know how much drag his boat has at a few different speeds (then we can interpolate to find the values at any other speed).

What would be so wrong with actually measuring the drag? It would be so easy, and the answers to all questions would be "right there" - no guessing, no calculating.

I understand the relationships but I’m not an engineer.

I’m suggesting an approach to quantify available subjective data.

If the poster has a vessel profile placing him in a borderline situation for positive performance in the projected conditions…then a second path is finding another vessel !

I see fishing kayak photos equipped just under the radar. I haven’t tripped over one on the water. I must live right.

From the photos you could believe all propulsion problems short of the Bay of Fundy are solvable by sending an email or showing up with a wad of cash.

Excuse, I have to go thru the morning arm and wrist exercises.

gas more practical
A few days ago I was out paddling and came across a guy who had an inflatable pontoon fishing boat rigged up with two gasoline weedeater motors. He was carrying a pile of fishing junk and he was no lightweight himself and that little craft moved right along upstream against a substantial freshet current. I would imagine that one of those weedeater motors would probably push a canoe quite well.

Looking for an example, quickly found a ‘canoe’ skiff:


leading of course to:


Gheenoe’s are common around Florida often seen crossing rough water on fishing runs.

Gas IC works well with fishing as gas doesn’t ‘disturb’ fish as kayaks do.

drag a log behind and your in, right Magooch ?

Not sure where you’re going.
I haven’t the foggiest idea what dragging a log has to do with fishing, and I don’t know what you’re trying to say about gas engines and kayaks disturbing fish. You’ll have to interpret.

the Long View
towing a log raft on the Columbia ?

I have a cartoon…I’m paddling past 6-7 fishing boats bristling with rods, tossing beer cans…

fisherman yelling


Yes but on paper. I hold that one drag coefficient covers all standard canoes 16-18’

link: http://goo.gl/J2VbwO

I have similar areas where water runs out and tide runs back but can you ? Manatee Springs State Park and a County park with hard running springs with manatee.

But a threshold situation requiring calculation.

Long way back upriver: eddy travel.

What good is that link

– Last Updated: Jun-05-14 8:19 PM EST –

That link takes me to a long list of articles. In the first five pages of the list, none of them had anything to do with speed versus drag/thrust in canoes of this type (only one even had anything to do with boats, but a very different type of boat going very different speeds), and certainly nothing backing up your premise, so I didn't continue after that (experience suggests that if you don't find the desired info near the top of the list, it's probably not there. Besides, it's up to YOU to do your own research, not me or anyone else here). No matter what one's choice of key words when making a search, one WILL get a list of articles as a result, but on the face of things that gets you nowhere. As I said in another discussion with you, you can't back up a dubious claim simply by supplying an endless list of irrelevant articles. It's important to realize that the mere fact that your chosen keywords created the list doesn't ensure that anything within the list is helpful to your cause.

Anyway, back to the point at hand. I don't accept the idea that all canoes have basically the same drag/speed relationships. Large differences are easy to find even among general-purpose (relatively non-specialized) solo boats. For example, if I wanted to paddle 12 miles against a brisk current on a particular river I know (I'm thinking of an upstream trip that's very familiar to me), I'd have good results with one of my solo canoes (and I wouldn't even be tired afterward), would work like hell with another and also be on the river much longer than I'd like, and would never make it at all in the third before my muscles gave out (though somebody a lot stronger than me could make the trip in that third boat, I don't think I could). Throw in some more-specialized designs and the range of effort needed to make the trip in various solo boats would be even greater. Switch to tandems, especially loaded tandems, and the drag increase would be huge in relation to any of the general-purpose solos boats. That's why two people paddling a tandem aren't twice fast (also why they don't only need to paddle half as hard) as one person in a solo canoe. The tandem has lots more drag that must be overcome, and doubling the paddling power is approximately what it takes (I put emphasis on "approximately" to satisfy the really good solo-handlers of tandem boats, but no one will argue the general idea here).

To build on my idea that all canoes do not have roughly the same drag, even if that notion were true it's not an idea you can work with because we still haven't found any published drag data for tandem canoes, just sea kayaks. And since you already tried to claim the validity of sea-kayak drag data, the fact is, a solo paddler in a loaded tandem canoe wouldn't have prayer of keeping up with someone in a sea kayak (using a solo paddler in this comparison is to ensure the propulsive power for the two boats is similar, as that's the issue at hand), and the difference is SO huge in this case that it would show up within the first few feet of travel, let alone what the difference would be after miles and miles. For any given level of motor thrust, the same proportional difference between those two boat types would occur (because it's still an issue of thrust vs drag, no matter how much you initially tried to obfuscate that fact). That should tell you that the drag data for sea kayaks is of no use at all in this case, to the point that any calculation involving speed or travel distance would be "off" by some sizable multiple of the true value (at least based on any reasonable estimate based on apparent drag differences. Quantifying the difference would give as a more accurate figure, but there can be no doubt that the difference would be way too great to ignore).

That covers the situation pretty well. I've offered a very practical and easy solution that any two people with a motor-powered boat and a few minutes of time on the water could accomplish. Nothing you've said, in all this vague talk of unspecified methods of calculation, gets us around this basic aspect of the problem.

THE PROBLEM is the posters. We’re here for an overview and offering educational searching. So maybe the poster can find his way.

For sure I’m not powering an electric boat. NO WAY !

No sail (not today)

I find many not up to assembling a common language search for their problem, if they have one.

Looks like a water quantification in watts would transfer from land or poached off the Navy.