Dennis,
I can't get the kind of performance I want out of a MK-RT101 by changing the prop. Minn Kota techs say: increasing the prop load is a good way to burn out the lower end (motor, not controller).
Let me try to explain this one more time.
Because of the low RPM range and prop limitations inherent to the Minn Kota motor, I don't want to use that lower end. I want to get an Etek-type motor rated at 48 volts, and operate it at 70% power by feeding it 36 volts through the 36 volt Minn Kota controller. The Etek-type motors generate more torque and higher rpms at 36 volts than the MK lower end does. I can get the performance I want out of an Etek motor fed 36 volts: that's why I want to use it.
As I see it, that combination won't burn out the controller, it will only make the engine run slower than maximum 48-volt speed, and that's fine with me.
The motor will only get the voltage and amps the controller will allow. If that's not enough to turn the motor at top speed, fine. But I don't see how that can burn out the controller, since it's operating in volt /amp ranges it's designed for, and there's no way the motor can draw more power than the controller will provide from a 36 volt battery pack.
If you can show me how using the 36 volt controller to pump 36 volts into an Etek motor (rated at 12, 24, 36, or 48 volts) will burn out the controller out, please do.
Otherwise, can anyone else in this group understand the system I'm describing, and say whether or not it will burn out the controller; and if so, then why? I'd sure appreciate it. Thanks.
Best Regards,
Kirk
--- In electricboats@yahoogroups.com, "dennis wolfe" <dwolfe@...> wrote:
>
> Kirk,
>
> If you MK 101 still works, all you need to do is change the prop, not the motor. The power output is determined by the controller, not the motor.
>
>
> ----- Original Message -----
> From: Kirk Mason
> To: electricboats@yahoogroups.com
> Sent: Saturday, October 09, 2010 6:16 PM
> Subject: Re: [Electric Boats] Controller question
>
>
>
> Thanks for your reply, Dennis. It helps.
>
> I'm not trying to drive a Minn Kota motor with other props; I want to combine a Minn Kota 36-volt controller with an Etek or Mars-type 48 volt motor. Haven't decided on the prop yet, but the first one I have in mind is a three bladed 11 X 9.
>
> But your reply does gives me good information to work with. Sounds like I don't want to exceed the amp draw or I'll burn the controller.
>
> I'll look around to find out what the amp draw is for the Minn Kota 101 at 36 volts, and compare that to the same spec for the Etek or Mars motor. (I think they pull about 140 amps at 36 volts, but I have to recheck that spec, too.)
>
> I'll hit "send" on this and go searching for the specs on the MK-101. Thanks for the lead.
>
> Back with more when I get more specs.
>
> Best Regards,
>
> Kirk
>
> --- On Sat, 10/9/10, dennis wolfe <dwolfe@...> wrote:
>
>
> From: dennis wolfe <dwolfe@...>
> Subject: Re: [Electric Boats] Controller question
> To: electricboats@yahoogroups.com
> Date: Saturday, October 9, 2010, 8:36 PM
>
>
>
>
>
> Kirk,
>
> You are missing the fundamental point, that is the controller puts out X power and that is all that is available to drive the boat, regardless of the motor it is connected to. A larger prop on any motor will pull more power, make your boat go faster and maybe ruin the controller.
>
> The controller, motor and propeller all must be balanced to work together.
>
> The voltage and motor type determine the RPM, the prop and boat resistance determine the load at that RPM (amps). The controller varies the voltage to the motor and therefore RPM.
>
> If I were you I would experiment with different props, all the while carefully monitoring the amps the motor is drawing. Do this with the boat running free, not tied to the dock.
>
> Your first check should be with the stock prop, the boat tied to the dock and controller at wide open. That is the amp limit you should not exceed with your experimental props and boat running free.
>
> Model airplane props are cheap and can be easily modified to work on a trolling motor.
>
> You will also find making a fairing for the round motor shaft will help more than you could imagine.
>
> Details of my walk down this path here:
> http://www.boatdesign.net/forums/boat-design/efficient-electric-boat-27996-15.html
>
> Start with post #212
>
> Denny Wolfe
> www.wolfEboats.com
>
>
>
> ----- Original Message -----
> From: gentlemancaller2009
> To: electricboats@yahoogroups.com
> Sent: Friday, October 08, 2010 8:13 PM
> Subject: [Electric Boats] Controller question
>
>
>
> Shouldn't the controller from a 36 volt Minn Kota Riptide 101# trolling motor be able to safely supply up to 75% power to a 48-volt Etek-type motor?
>
> I'd like the groups opinions before I try it.
>
> Thanks,
>
> Kirk
>
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