Re: [electricboats] Trolling Motor Propellers

I feel an urge to jump in on this discussion but lack the EE knowledge and experience.  Allow me as briefly as possible to say what I've done and invite anyone who is barking up the same tree to contact me, if desired.  I have been messing with elect. trolling motors for a while now.  Mostly on small, "creek boats" as we call them in SE NC.  A few years ago I ended up with a Redwing 18, needing power.  The recommended power is 10 hp. outboard.  Being elect. inclined,  I fab'd up a couple of 82# Motor Guide's into duel outboards.  The prop I chose was the orginal Torqeedo.  2 of them, modified to fit, both right hand thrust.  I did not believe it untill experienced but the thing took 3X as long to turn left as right, (may have that reversed) and would not manurve very good, (one reason for duels).   I have spent the last 2 years and some $$ getting a left hand matched prop.  Scanned/flipped/3D printed.  It works.  Has minor issues but they can work out.  I'll attach a couple of photos and just ask, "anyone interested"?

thanks,

Glenn Holland/ gholland1@nc.rr.com

From: Ken Cooke

Sent: Sunday, February 02, 2020 2:35 AM

To: electricboats@groups.io

Subject: Re: [electricboats] Trolling Motor Propellers

For these little electric off the shelf trolling motors, To fit the prop to your boat, you just have to do some "sea trials".  Buy a range of props between 4" pitch and 7 with different diameters" pitch and test them out one at a time with a GPS and Amp Meter.  (They are cheap enough to order by the dozen)

The one that gets you closest to your boat's Hull Speed with the lowest power drain without exceeding the amp rating of the motor is the one for you, then you can start ordering those specific props going forward.

Regarding "Burning out the motor"

I have also found you don't burn out the motors, you burn out the control boards first.  (i've burned out 3 control boards in my experiments) I swap out the control boards and the motor continues to function just fine.

If you are using non-stock props on your craft best to keep an Amp Meter handy to make sure you don't exceed the published power rating at different power settings.

For example, Minn-Kota 12V 50# Thrust motors have a 50 amp max power rating.  (Usually there is a "loose" relationship between the Pounds Thrust rating and the amp ratings.  (That's different for 24 - 48 volt stock trolling motors)

Switched VS Pulse Width Modulation (PWM) Motors
Not sure about Motor Guide, Haswing, etc...  But, with the Minn-Kota motors their Endura C2 Models (Cheapest, stepped switches) have a different amp rating per switch. 

My estimates for the Endura C2 12v 50# Thrust Model are

• Setting 5 50 Amps,
• Setting 4, 20 Amps,
• Setting 3, 15 Amps,
• Setting 2 10 Amps,
• Setting 1, 5 Amps.

You can run just fine full throttle (Switch 5 Power Setting)  with a higher pitch prop (50 amp max)*

But step it down to switch 4, it's capacity is only 20 amps. If your load is pulling 24 amps at that speed setting, then before long you will start smelling that tell-tail whiff of melting plastic as the wiring insulation starts to cook, followed by smoke coming out the wire ports and handle socket, then, if you keep it up, see fire as it lights up the plastic housing.

The EndruaMaxx models use PWM control boards as opposed to switched circuits.  So, I am confident it can handle the full amp ratings no matter what the speed setting.

Another precaution I take when running full throttle on either the PWM or Switched models is to stop every hour for at least 6 minutes to let things cool down a bit. The Relays get really hot.  I found my PWM Control board returns to ambient temp after 6 minutes of rest.

Machining the plastic props:

The APC 4X10P-LH prop comes with a sheer pin slot already cut.  You may have to drill out the center hole to fit your shaft. 

If you order other sizes you will have to do some drilling/grinding modifications for the shaft hole to fit and to create a sheer pin slot.

cpcanoesailor is a better machinist than I.  I had a difficult time getting the center hole and sheer pin slot properly ground/drilled properly, so my prop would vibrate at high speeds if it wasn't spot on centered/leveled.  (And you really don't know if you got it right till you mount the prop and get underway under load)

Since I swap out the little plastic props after about 10 hours of use. (Sooner if I hit something) that drilling/cutting shear pin slots got a bit tiresome.

Thanks,

Ken Cooke

Lexington, KY USA

On Sat, Feb 1, 2020 at 9:06 PM sw via Groups.Io <v1opps=yahoo.com@groups.io> wrote:

Some one said 10x4 or 4x10??

Also heard If not matched right it will burnup the motor

On Friday, January 24, 2020, 09:16, cpcanoesailor via Groups.Io <cpcanoesailor=yahoo.ca@groups.io> wrote:

Keith, I used an APC 11x6 RC airplane prop with a Haswing 55lb thrust 12V brushed trolling motor. It pushed my 6m proa (outrigger sailing canoe) about 20% faster than the stock 3 blade prop, using the same amount of power. Even though the prop had narrow blades, I found it to be durable enough. No noticeable damage from normal use in salt water with occasional wood bits floating by. I added a nose cone that matched the motor housing diameter, with the prop inside, to reduce resistance. I machined the prop using a drill and metal file to enlarge the shaft hole and cut a slot for the motor's drive pin in the rear face of the prop.

As an alternative to rewiring, you may be able to reverse the direction of the handle connection to the vertical shaft on your trolling motor so the prop is at the front. I did this with my new brushless 1.0hp electric trolling motor (another Haswing).

I did find some slippage when accelerating to full speed from a dead stop, but no evidence of cavitation.