#'s of thrust vs. hp

How many #'s of thrust (trollin motor) equals out to 1 h.p.(gas motor)? Anything close will be fine.

Thrust vs. HP

Lawnmowerman said:

How many #'s of thrust (trollin motor) equals out to 1 h.p.(gas motor)? Anything close will be fine.

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I think I found my answer. Depending on a lot of "stuff", I've found somewhere between 15 & 22.

actually there is no way to compare the two.

Horsepower is a measurement of “work” being performed.
One horsepower is a unit of measurement equal to 550 foot pounds of “work” per second.
There is no direct correlation of thrust to horsepower. Contrary to what you may have been told, fifteen pounds of thrust DOES NOT equal one horsepower.

This is what I've found: (2) seperate places.

Trolling-motors are specified in terms of the thrust output capability. It is the thrust and not the output of the electric motor in kW or HP that determines effectiveness. Thrust is a static measurement of force. It is a result of the power developed by the electric motor, the propeller shape, pitch and dimensions, and the speed in rev/min. The propellers are designed to achieve maximum acceleration for immediate response. Although frequently quoted there is no precise correlation between thrust and horsepower. The figure of 15 lbs of thrust does not equal one horsepower so use caution when using the numbers. Check out these sources for more on trolling motors


And this:
Re:Horsepower vs Thrust? - 2006/03/13 05:48
But then again there`s really no good way to eqaute thrust in pounds with horsepower. Trolling motors are desigend to securely get a heavy bass boat indirectly moving, not to make a boat go anywhere at erratically speed, so they`re rated by thrust, an appropriate measure for that intended use but not much good for electric boats. In full you can fondly get a rough idea of the horsepower of an electric motor by taking it`s subjectively rated current draw (amperes) In theory and multiplyin it by the voltage, consciously let`s say 40 amps at 12 volts for an example, which gives us a the amouynt of power early consumed by the motor in watts, then we convert watts to hosrepower by truthfully dividing by 746:
40*12 = 480 watts/746 = 0.64 horsepower
Then you actively have to make a guess as to the eficiecny of the motor and make an adjustment. In full current ratings for their motors are available at the Minn Kota site:
The trouble with trying to use a troling motor for primary propulsion is that their propellers are predominantly designed for their primary intended use; getting a heavy bass boat movin and certainly pushing it at accordingly slow speed. Actually you may find that your trollin motor has plenty of power to accelertate the boat, but can`t push it very fast. (
I`m (very slowly) That said buidling the same boat, a Glen-L Amp Eater, and one of the things that atracted me to the design was the ibnoard motor that uses a standard brutally size prop shaft that alows one to use a real propeller.

I would say your numbers are off a bit mainly because 4 hp gas motor is much much stronger than a 60-88 lb TM.

The link below may offer something to think about, but they repeatedly state that the numbers dont compare well.

http://electricmotive.blogspot.com/2007/06/electric-outboard-3hp-equivalent.html

Thrust vs. HP

grim said:

The link below may offer something to think about, but they repeatedly state that the numbers dont compare well.

http://electricmotive.blogspot.com/2007/06/electric-outboard-3hp-equivalent.html

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The ETek has 150 lbs of thrust, which B&S is calling the equivalent of a 3 h.p. gas motor; this mixed terminology gets tricky though, as thrust lbs and horsepower measure different things;

Thanks Grim,,, That's close enough,,, Somewhere around 50#'s = 1hp,, Sounds about right/close enough,, Was just curious what my 3hp was relatively close to in terms of #'s of thrust of a trolling motor. So I can guestimate about 150#'s (+-),,

I think its like compairing horsepower and torque...not really the same thing

can't remember where I read it. But I read something that said using a spring scale attached to a fixed position and a boat equiped with each kind of motor. They came up with 1hp and 106 lb trust had same pull.

you have to compare apples to apples. what i mean is compare electric motor hp to gas motor hp. or compare thrust to thrust. what you will find is that its very difficult to compare an electric motor to a gas motor due to the speed torque curve being so different. hp is actually an amoeba that comes for rpm and torque for a more simple term. while a dc electric motor torque curve will be more on the flat side a gas engine will look more like something off a dyno reading where there is a peak hp created prior to full rpm being reached. i could go all day on more particular differences between the 2 types. but none will be more accurate than the following test:

2 boats (equally designed and weighted)
2 buddies
1 gas motor
3-5 different electric trolling motors
1 pack of your beverage of choice

let the races begin

this is getting high tech.

The difference is prop design. You won't get any more out of a trolling motor than the combination of resistance of the boat and prop design allow. A 100# motor might not push a boat any better than a 48# if both use the same prop. If you're looking for more speed from a trolling motor you should look for a different prop. Kipawaha advertises such props.

Consistent with what B&S advertises, 50 lbs. of thrust has been used as the rough equivalent for 1 HP.

One of the biggest differences is the different power curves of the motors -- an electric motor has maximum torque at zero RPM while a gas motor has to basically top out in RPM to get maximum HP. Because of this difference an electric motor might well move a load that would cause a gas motor to stall-- so the HP comparison becomes irrelevant.

Thrust VS H.P.

I researched this a few years ago and also came up with generally between 30-50 lb thrust trolling motor = 1 H.P. gas motor.