I have a Minn Kota Endura 50 that I have been using in Salt water now for
about 2 yrs. A long time ago I did a report to potter group indicating my
use as follows:
Test Conditions for Endura 50 conducted on canal to ICW in Florida.
Average canal depth during test 12' Some sections of canal had current flow
of 3 mph. The average wind speed was 8 MPH.
Distance from ICW to end of canal - 2.1 miles
Round trip Sailable distance over which tacking against wind is possible = 1
mile
Average wind speed 8 MPH
Widest section of canal distance .5 mile
Sailable distance on reach/run 1.1 mile
Sailable distance close reach .6 mile
Test of Minn Kota Endura 50 mounted in center stern position of Sovereign 13
( 375 lb sailboat) attached to EverStart Marine starting Deep Cycle battery,
Part # 29hdp-6, series 27, 875 cca, 205 min reserve capacity - I purchased
this 120 AMP. battery at Wal Mart. Battery is 10 ft. from motor and there is
a 10' section of 10 awg copper wire added to motor to reach battery. Wire
gets warm when motor is run at throttle position 5
This Test was performed before full tide swing.
Total distance traveled 2.69 miles per Garmin GPS 12 at Throttle setting 5.
Speed against current 3.3 mph average per Gps12
Speed with current 5.6 mph per Gps12
Slowest speed against current 1.9 MPH
Fastest speed against current 3.6 MPH
This test performed in same direction, same section of canal where current
was less than 1/4 mph...
Maximum speed with tester sitting in bow 4.6 mph sustained 3 minutes with
some bursts to 5 MPH. Maximum speed with tester sitting at stern by motor
4.0 mph sustained 3 minutes Effect of moving weight (me) forward to bow -
increase speed .6 mph
Average speed @ throttle position 4 was 3.3 mph (15 min test) this changed to
an average speed sitting in bow of 3.9 mph (15 min test)
Maximum average speed after 1 hr of use at throttle position 5 while seated
at stern - 3.9 MPH Total time to recharge battery after test (1 1/4 hrs) 2
hours @ 15 Amp charge rate.
Conclusion:
Maximum speed attained 5.2 MPH burst in section with 0 current and 0 wind.
Maximum sustainable speed over 15 mins. with Minn Kota Endura 50 is 4.0 mph
When racing you should sit in bow of sailboat to maximize speed.
Maximum range at position 5 of throttle is 10 miles or 2 hrs.
Maximum range at position 4 of throttle is 20 miles or 4 hrs.
Speeds under position 3 are not usable by me. I like to get there...
Size of wire used to carry battery power to motor affects max speed of motor.
I should use AWG 8 or less wire to run wire from batt to motor (12').
Speed is affected by wind speed. Heading into 8 mph wind slows boat down by
1MPH.
Best
SF
In a message dated 5/10/00 8:36:04 AM Pacific Daylight Time,
ChrisSayer@StratfordGroup.com writes:
<< Mark -
I have been using one of the smaller MinnKotas with great results. Mine is
the Endura, essentially a budget motor in the 32-36 lb thrust range. I
couple that with a 31 amp hour gelcell battery. The chart shows me getting 1
hour at full power, which equates to a roughly 3 mile range (My P15 shows 3
- 3.5 knots on GPS at full power, NO WIND) In reality, I typically run it 30
to 40 minutes at "3" during the course of a day on the water, and have yet
to run it out. Yes, I also carry a paddle, and try to avoid getting too far
downwind from my launch point.
At last weekend's Ditch Run (BTW - Thanks to all who put that on), I motored
at full power upwind (5 knots?) about a mile and a half, and still had
plenty of juice left. Dave Kautz had loaned me his gelcell, so I had a
backup. (Thanks, Dave)
My battery sits in the cockpit, below the tiller, where it is generally out
of the way. If your Potter still has the locker in that position, it might
be an ideal place to stash the battery. When performance is an issue, I have
disconnected the battery and placed it in the cabin for better weight
distribution, but being a P15, it usually isn't an issue. (Or is perpetually
an issue, depending on your point of view.)
Hope a few extra insights help. From what I saw of your post, I would guess
that you would be very happy with the electric option. If I had it to do
over again, I probably would have tried to swap the motor that came from IM
for some different options.
Enjoy!
Chris Sayer
P15, #2380, Akala
San Jose, CA
-----Original Message-----
From: hlg@pacbell.net [mailto:hlg@pacbell.net]
Sent: Tuesday, May 09, 2000 9:30 PM
To: WWPotter@egroups.com
Subject: [WWP] Re: Minnkota motors
Hi Mark,
Welcome to the group. It's hard to answer your question without knowing
what kind of conditions you could encounter in your area. I love my
electric, and so far it has served my purposes. I just wanted to
experiment with electric propulsion to see what was possible, and I
invested more than you might want to by getting the MinnKota Riptide
RT70/S, which has 70 lb thrust and runs on 24 volts. The lower thrust motor
you named may serve your purposes. There is a 55 lb thrust Riptide that is
probably essentially the same as my 70, but only requires 12 V.
To get some idea of the power a given electric motor will actually provide,
ignore any optimistic thrust-to-horsepower conversion factors you might
find. Multiply the max ampere (A) draw of the motor times the operating
volts (V). That will give you the number of watts (W) going into the motor.
My motor uses 45 A maximum at 24 V, which equals 1080 W, approximately 1
kw. To convert watts to horsepower (hp) you divide by 746, which means the
power going in to the motor is 1080/746 or 1.45 hp. Obviously, the motor
cannot produce any more power than is put in to it, which means my 70 lb
thrust motor produces something less than 1.45 hp at the max power setting.
For comparison, most Potter 15s use gas outboards rated at 2 to 3.5 hp. My
observation is that the 1+ hp is about right, as compared to my 3 hp
Seagull.
The Riptide series of MinnKotas are the saltwater versions, probably a good
idea since you will be running in saltwater. The engine seems pretty
rugged; I've run it into things occasionally with no damage. Another
feature of this motor and most of the higher priced MinnKotas is
"Maximizer," which means that speed is controlled by pulse width modulation
and is infinitely variable. The cheaper motors use switched resistors to
provide a choice of five (I think) fixed speed settings. The Maximizer is
claimed to be much more efficient, which means better range, and provides
finer control with the continuously variable speed setting.
Since my motor requires 24 V, I use two 12 V batteries in series--two
#24-size, wet cell, deep-cycle batteries rated at 95 ampere-hours (Ah).
They fit crosswise in the cockpit footwell of my old first-generation
Potter, next to the forward part of the centerboard trunk, giving me 90 lb
of ballast low in the hull. At 100% power I would probably get less than 2
hr running time, but it appears I can get twice that at 50 to 75% power. So
far I haven't run out of battery power, but I sail when I can and rarely
use max power except to get up to steering speed quickly.
It moves out impressively at 100%, but doesn't have the push of my 3 hp
Seagull. I've built in wiring for the motor using 4 AWG marine cable with
crimped and soldered connections for minimum voltage drop.
I would prefer not to have to worry about possible acid spills, but the two
types of nonspill batteries are more expensive, larger, and heavier for
equivalent output. I bought Costco's Kirkland-brand deep-cycle batteries at
40-some dollars a piece. The 95 Ah rating is better than most #24 size deep
cycle batteries, which are commonly rated at 85 Ah.
The motor has a chart printed on it that shows running time at different
power settings:
100%: 2 hr
75%: 3 hr
50%: 6 hr
25%: 12 hr
10%: 20 hr
The chart doesn't indicate what capacity batteries are being used, but the
manual recommends at least 100 Ah, and the charted running times are about
what I observe with my 95 Ah batteries. At 25% though you might not be able
to maintain steerage, and at 10% you can count the propeller revolutions,
so the 12 hr and 20 hr numbers are probably not meaningful for a Potter.
The speed at 75% power is comfortable but less than you would probably be
cruising in a gas outboard. The speed at 50% is okay too if you're in a
laid-back state or trying to stretch the range. Most of the time I'm
running between 50 and 75%.
Three of the friends I sail with have 36 lb thrust MinnKotas, which are
usually adequate for getting in and out of marinas, but don't seem to do
well in a wind. I found I could maintain 3.5 kn directly into a 15-20 kn
wind with my larger motor. The Potters have a high freeboard and are
affected more by the wind than a low profile bass boat might be. Add some
chop or current and you may find it just won't make it, even at max power.
That could be true of my larger motor also. So far I've avoided situations
where I would have to motor any distance in windy, choppy conditions with
the MinnKota.
If you camp in your boat's cabin, some accommodation will have to be made
for the batteries, at least as mine are installed. The one time I've slept
in the boat since I've had the batteries, I placed cockpit cushions under
the bunk cushion in order to get a reasonably level mattress. A better
method might have been to temporarily move the battery. I've also
considered building a higher, lightweight bunk deck above the original
level. Since the hull is wider there, the bunk width could also be
increased.
That's probably more than you wanted to know, but I'm enjoying the
experiment and am glad to share my experience with smooth, silent running
electric propulsion. Let me know if you have other questions. You might
also check the web sites listed in the "Links" on the Potter Yachters web
site <http://potter-yachters.org>.
Harry Gordon
P14 #234, Manatee
Propelled by gunter rig, lateen rig, electric power, or Seagull
Mountain View, CA
>Hi Harry,
>I just joined the "Potter Club" with the purchase of a 1979 P15. My wife
>hates outboards because of the smell, noise, gas danger, ect..... (me too)
>so I'm toying with a Minnkota 40-48 lb thrust. what do you think? Have you
>been happy with yours? Would you go the electric route again? How long
>will a 100 amp battery really last? We plan to use it only for getting to
>and from the ramp about a 1/2 mile or as back up if the wind dies on us.
>We mostly hug the coast line of Long island Sound.
> Thanks,
> Mark
> P15 #813
> "Holly Ann" (I think, still deciding)
>>
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