Trolling motor amp draw question

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OUTLAW
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Trolling motor amp draw question

Post by OUTLAW »

Trolling motor on a kayak yadayada..,toss up between New Vessel 36 ( because it’s advertised as saltwater) or Minn Kota 40 fresh water.
Would a minn Kota draw less amp due to innovation or are they about the same?
NV has good reviews but I’m kinda thinking the MK may be quieter, no real basis other than years of advertising.
The head and controls will be dissembles anyway, but will the motor unit hold up in saltwater? Are they made that much differently?
Thanks


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kickingback
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Re: Trolling motor amp draw question

Post by kickingback »

The higher the pounds of thrust the more amps it will draw. Also the Tm will be heavier the higher you go. You will be able to move faster with a larger pound thrust motor though.
You will need to look at the specifications for each motor to see how many amps they draw an hour. Then you need to figure out how long you keep it "wide open" to get the amp draw you need. It gets math complicated but you can get an idea how much you need.
It is all about the weight and balance issue the higher you go as well as how much battery power you will need.
I found by going to a higher TM (from a 24 to a 30) it got me to where I was going a bit faster which means I can hit more areas in a single trip. I also have a 120 Amp Hour, 66 lb sealed AGM battery to power it so I can go 12-15 hours easily on one charge. I would say half my use is full speed getting to other areas. That's how I figure my time out. When I get home from 12 hours my battery is only 46% charged before I start charging again. Never been below 25% on my AGM as I don't want to drain completely as I heard it can effect performance over time.
As for salt water and fresh water TM's, they advertise salt water have an extra seal and use only stainless steel parts. But all TM's are sealed for water period so the stainless issues is the only thing you need worry about AS LONG as you wash the TM off after each use in both salt and fresh.
My 24 Watersnake was advertised as saltwater ready but my Bass Pro 30 lb was not and I have not had any issues with the 30 lb as long as I keep cleaning it after each trip.
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Crusader
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Re: Trolling motor amp draw question

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In my experience minnkotas were fine. I went through 2 of them in 3 years -- in both cases they died because I got braid in the prop and it ruined the seal. Once you get a line in it -- gotta take it apart, clean it and replace the seal.

It is unlikely innovations can significantly increase efficiency of electrical motor -- energy losses are already very small. Note that speed and power draw are related in non-linear way, you probably need 3 times more energy to increase your speed from 2mph to 4mph.

40lb tm is on upper boundary of kayak power requirements -- unless your boat is a barge you'll probably going to throw wakes at top speed :-)
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TexasJim
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Re: Trolling motor amp draw question

Post by TexasJim »

You want to reduce the amp draw on your trolling motor for a kayak? Change the prop! A 40# trolling motor is designed to pull or push a 2000 pound bass boat. You have a kayak maybe 400 pounds at the outside. So, you don't need a wide, big pitch prop. Guys on this Forum years back started using model-airplane props on their yak trolling motors. Equal speed to the original, but seriously reduced amp draw. I put a 40# Minn-Kota TM on my Perception Pescador, with a 12-inch model airplane prop, trimmed to 10" dia, with a 35 amp-hour AGM battery. It zoomed, and I never got the battery below 12.5 volts! I didn't want to title and register my yak, so I put the TM on my 12-foot aluminum skiff, maybe 400 pounds max. The same TM with airplane prop pulls my skiff around for hours and never have I come back home with less than 12 volts.

It's all physics. The greater the mass, the more energy is required to move it. Less mass, you can get there with less energy. Using a skinny, large diameter prop with a lighter load will result in more speed with less energy consumption.

For me, I really didn't want to put a 65-pound battery in my 60-pound kayak! Group 24 and Group 27 batteries are seriously heavy. YMMV TexasJim
OUTLAW
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Re: Trolling motor amp draw question

Post by OUTLAW »

Great info. Thanks guys


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TG05
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Re: Trolling motor amp draw question

Post by TG05 »

Check out the Bixpy water jet. https://bixpy.com
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Crusader
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Re: Trolling motor amp draw question

Post by Crusader »

TexasJim wrote:It's all physics. The greater the mass, the more energy is required to move it. Less mass, you can get there with less energy. Using a skinny, large diameter prop with a lighter load will result in more speed with less energy consumption.
It depends... Basically, you spend energy on:
- accelerating the boat
- overcoming friction (and other forces) in various parts of the system (inside the motor, prop vs water, boat vs water)

by changing prop you change only two aspects of your system (at the same boat speed) -- prop interaction with water and friction inside of motor (if it's rotation speed changes). What you say could be true if energy spent on dealing with these aspects is significant part of overall "energy budget" and changing prop reduces that part. Seems unlikely to me, but I might be wrong -- power draw of electric motor drops with increase of it speed of rotation (it is also a generator).
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kickingback
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Re: Trolling motor amp draw question

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I saw the new Bixpy 1000 get one of those new two pontoon boats with a deck and the chair sits high and you can still pedal it like a bicycle. It had the craft going well over 6 mph at full! It was cooking!
Wind, water, propeller shape and number all can make a difference in speed and thrust overall or how fast you get up to speed. Many YouTube videos. One guy is adamant and gets lithium batteries to try out for tournaments for his setups and records for the sponsor. That's the way to do it.
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