Re: [electricboats] Trolling Motor Propellers

I really like the look of this Redwing and how you've rigged the electric motors.

I converted a Macx 26 to solar with two 12v 55# thrust motors and would second your concern about having enough thrust to fight a 15 knot wind or 2+ mhp current or 2' swell so carry an auxiliary 9.9 gas outboard with me for the tough spots.

In discussing using trolling motors for "primary propulsion" have you figured out why Minn-Kota, MotorGuide and others use # Thrust as their measure of power and WILL NOT publish their Horsepower equivalents?   

The answer is simple, marketing. 

80# sounds so much better than 1.2 hp.  or in my case 55# sounds much better than 0.7 hp.

The second specification you won't get from these trolling manufacturers is RPM ratings. 

You might catch a tech in a weaker moment of honesty admitting the top RPM is around 1500 at Wide Open Throttle.  From there, you can calculate theoretical top speeds given different prop sizes.

With an Amp Meter and voltmeter (in line or clamp) you can get at energy used and tune various prop pitches, diameters and blade widths to your boat.  

I've stumbled across some model airplane props that really improve the efficiency of my little trolling motors over stock props. 

For example, on my craft,  a 55 12v burns 31 Amps at 12.8v at Wide Open Throttle (100%) with an APC 4" pitch 10" LH Pusher Prop.   The stock Minn Kota Weed Wedge prop would burn 47 amps at the same voltage.

Here's the fun part, the Model Airplane Prop actually pushes the boat 0.5mph Speed over ground faster than the stock prop even though it's consuming less power at those rates.

We've discussed the advantages and disadvantages of the model airplane props on this forum before.

-Cheap ($5.00 each shipped)  VS Flimsy (Drag it across a gravel bar and you will need to change it right then)

I don't have to deal with weeds, so the Model Airplane Props may not deal with weeds as well as the stock props are designed to do etc....

Burning 300 watts per motor, I can push my Mac26x at 3.5mph all day with a 1200 watt solar array in full sun and not draw a single amp from my batteries unless I go under a bridge, or it clouds up, or I run under the shadow of a tree.

Ken Cooke

Kentucky River USA

On Tue, Oct 20, 2020 at 9:46 PM Glenn Holland <gholland1@nc.rr.com> wrote:

Bill,  I don't know if you have seen a photo of my Redwing?  I have twin electric OBs hung off the transom, Motor Guide 80lb.@ so 160 total.  They are enough power for hull speed, about 4.5 mph.  I have Torqeedo props.  My challenge is manuvering.  With RH props, I have trouble with left hand turns.  I am fabing up a LH prop to match the RH Torqeedo.  That will solve the problem.  My one recommendation is to pay as much attention to your prop as the motor.  If you put one motor in the well of the Redwing, I would get a 36V. as big as possible.  I bought mine off Ebay and saved quite a bit of $$ for pratically new motors.  Make sure you get didgital/Varible/PWM.  That makes a LOT of difference in range.  I have been in up to about 10-12 kt. winds with OK handeling.  Please ask anything.  I'm not an EE but I've done  few things.

thanks,

Glenn

https://www.youtube.com/watch?v=Razo_PrsEyo

https://www.youtube.com/watch?v=wQUYf3dIQeo

From: wdr99 via groups.io

Sent: Tuesday, October 20, 2020 4:30 PM

To: electricboats@groups.io

Subject: Re: [electricboats] Trolling Motor Propellers

Hi Glenn,

I hope this note finds you well.  I have a Redwing 18 also and am interested in repowering with electric.  I'm interested in your experiences as I expect I'm going to approach this incrementally.  

I've been happy with the trolling motors I've used as kickers for small sailboats and so I expect to start there withe the Redwing.  I'd love an Elco or a Torqeedo but I'm concerned with the expense and either lack of reviews or mixed reviews as the case may be for such an expense.

Did you have experience with a single 80lb motor?  Also, did you have experiences with wind and waves?  

Thanks for any info you can provide.  

Bill in Duluth

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