Your last guess at horsepower is about right. The various 36 lbf thrust
MinnKotas use either 34 or 36 amperes maximum at 12 volts, so the power
input is approximately 12 V x 35 A = 420 watts. To convert watts to
horsepower, divide by 746, which gives you 0.563 hp max input power to the
motor. Naturally the power out is less. Still, 1/2 hp is probably about
right for comparing it against gas outboards.
I'm using a 70 lbf thrust MinnKota that uses a maximum 45 A at 24 V, which
equals 1080 W, which is 1.44 hp. It does pretty well but has subtantially
less power than my 3 hp Seagull outboard. I use two 95 ampere-hour, wet
cell, deep-cycle batteries in series (mine requires 24 V), located in the
cabin footwell, one on each side of the forward end of the centerboard
trunk.
A number of people on this list are using electric motors the size of
yours. The consensus seems to be that they are usually fine for getting in
and out of marinas and Pottering about on a calm day, but just can't hack
it if there is any substantial current, wind, and/or chop to contend with.
I suggest you try out the motor and see how you like it. For test purposes,
I would just buy or borrow a 12 V deep cycle battery or even use your car
battery (fully charged). Just set the battery on the cockpit floor and
connect the motor cables to the battery. If the motor doesn't have cables,
you can probably use jumper cables temporarily. Go out on a quiet day so
you don't have to worry about the battery turning over and spilling acid in
the cockpit, or wedge it in place somehow.
The lack of noise is wonderful but may give you the feeling that nothing is
happening. You'll probably be using full power to get the boat moving, then
you can back off to a lower setting to reduce battery drain. I love the
quiet, the positive control (instant on-off, faster-slower,
forward-reverse), and not having to mess with gasoline and oil.
If you like the electric, you'll probably want to do some permanent,
substantial wiring, and the battery will need to be contained and strapped
down. To maximize the power to the motor, you need to minimize the
resistance in the wiring and connections. I've installed marine (tinned)
AWG 4 wiring, and all the terminals are crimped and soldered. The running
time you get will depend on the size and number of batteries. A smart
charger is a worthwhilei nvestment so that your batteries will start out
fully charged and so their lives won't be shortened by overcharging.
I've used my Riptide RT70/S motor for about 4 hr without noticing any
slowing down. That was mostly at 50-75 percent power. My motor has the
Maximizer feature, which gives infinite speed control from 10 to 100
percent. The Maximizer uses pulse-width modulation instead of stepped
resistances to vary speed and is supposed to be more efficient. I can go 3+
knots against a 15-20 kn wind with my 70 lbf thrust MinnKota in smooth
water. If your MinnKota has continuously variable speed control, it has the
Maximizer feature.
If you routinely sail in an area of high currents and you motor a lot, or
motor long distances, you'll probably want a gas outboard, but keep the
MinnKota. There will be many occasions and places where it will be all you
need.
Naturally, it's a good idea to plan your trip so the currents are in your
favor. Even with a strong gasoline outboard, you will probably not be able
to make more than about 5 knots through the water.
I could probably have found a good gas outboard for what I've invested in
my electric setup (the MinnKota alone was $480), but I was intrigued by the
idea of clean, quiet electric power and just wanted to experiment.
Finally, you have a sailboat, so who needs a motor anyway?
Harry
P14 #234, Manatee
Mountain View, CA
>Hi folks,
>
>I recently "inherited" a brand new trolling motor from a family member.
>It is a Minn-Kota Turbo 65 with a "Weedless Wedge Propeller" and "36 lb.
>of thrust".
>
>Has anyone else tried a trolling motor on their Potter 15? My 4 HP
>Mariner took a swim (see my last E-mail) and is a total lost. I have to
>say I am quite tempted to try this trolling motor but was wondering if
>anyone else had experience with this? In particular, how does "36 lb.
>of thrust" translate to horsepower? What can I expect, 2 HP or even 1/2
>HP??? Also if you tried this before, how did you manage the
>battery/cable problem?
>
>With all I've been reading on this site, the idea of the extra weight of
>a battery in the chain locker sounds like a good idea (not to mention
>the loss of about 30 extra outboard lb. in the stern. Also, I like the
>ecology aspects of no noise or fumes or gas can. The problem is we have
>a tide here in the Charleston harbor that can be brisk at times, and I
>don't want to get caught out... makes me a little nervous to try it, so
>any experience, stories etc. regarding trolling motors on the Potter 15
>would be very much appreciated.
>
>Jeff G.
>Charleston, SC
>Potter 15 "At Long Last"