Re: Electric Trolling Motor

Gordon (
Wed, 4 Nov 1998 10:47:55 -0800

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West Wight Potter Website at URL
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>Right now I am in the process of replacing my 2 Stroke Outboard for a Electric
>Trolling motor, solar cells (mounted on the stern on a mounting horseshoe) and
>forward mounted deep cycle batterys, inverter and so forth. Will go well with
>my 12 volt Coffee Maker, Reefer, Propane BBQ Grill and CD player. So far the
>total cost for my boat is up to about 6 K but then again I have a LOT of
>creature comforts... <G>
>P19 Traveller
>Columbia SC


What trolling motor are you installing? I've just wired my P14 for a 70 lbf
MinnKota RT-72S (24 V). Hope to get it in the water today to try it out.
According to MinnKota's guidelines, this motor is overkill for a P14. But
most reports from Potterers indicate that motors up to 42 lbf thrust don't
hack it on a P15 when you get into wind or current, and I'm not sure that
this will either..

The rules of thumb for converting thrust ratings to horsepower seem
extremely optimistic (70lbf x 16 lbf/hp=4.4 hp) , but possibly the
horsepower ratings on outboards are also optimistic. It's obvious that I
can't get more power out of the motor than I'm putting in, which is a
maximum of 45 A at 24 V, or 1080 W. At 746 watts per horsepower, that is an
input power of only 1.45 hp, so there is no way the motor can produce 4 hp.

Anyway, I'll soon have a reality test. I'll be interested to learn what
motor you're using and how it works out. I now have two 40 lb, series 24
batteries in the cabin footwell, sitting in battery boxes on the bottom of
the hull next to the centerboard trunk. Should add considerable stability
but takes a lot of space in my small cabin. I still have to devise a
holddown system and cover to protect against shorts and acid. I used AWG 4
cable to connect from the batteries to the motor cables. I will later add
12 V wiring for lights, GPS, and such.

Harry Gordon
P14 #234, Manatee