On Apr 14, 5:50*pm, Jere Lull wrote: If you've got
the electric already, why not try it and see how it works? From what
you say, it sounds good enough, but only you can accurately assess
that. 30 pounds continuous could get our 28 footer moving at perhaps
a knot or two in flat water.
Jere Lull


I'll give it a try. Does anyone know of a formula to roughly
equate electric motors to horsepower? Would be curious as to the
horsepower equivalent of my Minn-Kota Endura 30. -J

On Mon, 14 Apr 2008 21:50:34 -0700 (PDT), Jay
wrote:

On Apr 14, 5:50*pm, Jere Lull wrote: If you've got
the electric already, why not try it and see how it works? From what
you say, it sounds good enough, but only you can accurately assess
that. 30 pounds continuous could get our 28 footer moving at perhaps
a knot or two in flat water.
Jere Lull


I'll give it a try. Does anyone know of a formula to roughly
equate electric motors to horsepower? Would be curious as to the
horsepower equivalent of my Minn-Kota Endura 30. -J

Yes. Pounds of thrust times speed in feet per second equals foot
pounds per second. 550 of them equals one HP. And its not 'roughly',
its exact. It is also true that 746 watts equals one HP.Thats rounded
off.

Casady

On Mon, 14 Apr 2008 21:50:34 -0700 (PDT), Jay
wrote:

On Apr 14, 5:50*pm, Jere Lull wrote: If you've got
the electric already, why not try it and see how it works? From what
you say, it sounds good enough, but only you can accurately assess
that. 30 pounds continuous could get our 28 footer moving at perhaps
a knot or two in flat water.
Jere Lull


I'll give it a try. Does anyone know of a formula to roughly
equate electric motors to horsepower? Would be curious as to the
horsepower equivalent of my Minn-Kota Endura 30. -J

Thrust is a treacherous unit for power. It needs an effective speed to
make it sufficiently specified.

30 lb thrust at 2 mph =
134 Newton at 0.9 meters/second =
120 watts =
1/4 HP (say)

But: 30 lb thrust at 4 mph = closer to 1/2 HP.

Brian W

Jay wrote:
On Apr 14, 5:50 pm, Jere Lull wrote: If you've got
the electric already, why not try it and see how it works? From what
you say, it sounds good enough, but only you can accurately assess
that. 30 pounds continuous could get our 28 footer moving at perhaps
a knot or two in flat water.
Jere Lull


I'll give it a try. Does anyone know of a formula to roughly
equate electric motors to horsepower? Would be curious as to the
horsepower equivalent of my Minn-Kota Endura 30. -J


The easiest way would be to find out much current the thing uses.

I*E=P, assume about 90% effeciency, so HP= (P*0.9)/746

If you want that in simpler terms HP= ((volts x amps)*0.9)/746

Cheers
Marty
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wrote:

The easiest way would be to find out much current the thing uses.

I*E=P, assume about 90% effeciency, so HP= (P*0.9)/746

If you want that in simpler terms HP= ((volts x amps)*0.9)/746

Cheers
Marty


Don't leave out the fact that the electric trolling motor power is
produced directly at the prop. There is significant power loss in a
gas outboard between where it is produced and the prop that does the
work.

Hmm, I don't really know, but I don't think the losses should be all
that big, one little water pump to turn, on set of crown and pinion
gears. Intuitively I don't think you'd lose more than 15%..

I'll bet that most outboard manufactures measure output of just the
head, no shaft, no water pump.

Cheers
Marty


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"Martin Baxter" wrote in message
...
Don't leave out the fact that the electric trolling motor power is
produced directly at the prop. There is significant power loss in a
gas outboard between where it is produced and the prop that does the
work.

Hmm, I don't really know, but I don't think the losses should be all that
big, one little water pump to turn, on set of crown and pinion gears.
Intuitively I don't think you'd lose more than 15%..

I'll bet that most outboard manufactures measure output of just the head,
no shaft, no water pump.

It would not be as much as that. 3-5% would be about the right amount.

wrote:
On Tue, 15 Apr 2008 18:36:10 +0200, "Edgar"
wrote:

"Martin Baxter" wrote in message
...
Don't leave out the fact that the electric trolling motor power is
produced directly at the prop. There is significant power loss in a
gas outboard between where it is produced and the prop that does the
work.
Hmm, I don't really know, but I don't think the losses should be all that
big, one little water pump to turn, on set of crown and pinion gears.
Intuitively I don't think you'd lose more than 15%..

I'll bet that most outboard manufactures measure output of just the head,
no shaft, no water pump.
It would not be as much as that. 3-5% would be about the right amount.

I think you're right Edgar, on a slightly larger motor, but two horse is
pretty small and the losses would be more significant, frankly I'd be
surprised though if they were more than 10%



I think it would be a bit more than that. The drive train has to turn
a 90 degree corner. And don't forget the power consumed by the
alternator, along with the already mentioned water pump. These things
add up.



Alternator? On a two horse?,

Cheers
Marty

wrote:
On Wed, 16 Apr 2008 13:38:02 -0400, Martin Baxter
wrote:

wrote:
On Tue, 15 Apr 2008 18:36:10 +0200, "Edgar"
wrote:

"Martin Baxter" wrote in message
...
Don't leave out the fact that the electric trolling motor power is
produced directly at the prop. There is significant power loss in a
gas outboard between where it is produced and the prop that does the
work.
Hmm, I don't really know, but I don't think the losses should be all that
big, one little water pump to turn, on set of crown and pinion gears.
Intuitively I don't think you'd lose more than 15%..

I'll bet that most outboard manufactures measure output of just the head,
no shaft, no water pump.
It would not be as much as that. 3-5% would be about the right amount.
I think you're right Edgar, on a slightly larger motor, but two horse is
pretty small and the losses would be more significant, frankly I'd be
surprised though if they were more than 10%

I think it would be a bit more than that. The drive train has to turn
a 90 degree corner. And don't forget the power consumed by the
alternator, along with the already mentioned water pump. These things
add up.


Alternator? On a two horse?,

Cheers
Marty


Suzuki DF4 and DF6 are both available with a 6 amp alternator

http://www.suzukimarine.com/sr_07/df6-4/features/

Ok, so twice the two horse, now the gear loss becomes less percentage
wise. Six amps, fourteen volts, is 84 watts, just a bit bigger than
1/10 hp, even at 80% efficiency, even if the alternator is actually
putting out the full six amps, still not not significant.

Cheers
Marty

When I started this thread I truly thought I had decided to either buy
a Suzuki 4hp or 6hp for my G3 Guide V14 aluminum utility boat;
however, with all of the good information I've received with the
variety of opinions I've trimmed it down to either a Suzuki 2.5hp for
$721, a Suzuki 4hp for $1008 or a Tohatsu 4hp for $833.

I believe the best "bang for the buck" is the Tohatsu 4hp 4-stroke and
I'll probably order that this week Here are the specs for it. Does
it sound like it'll push that 14 footer around the lake at a fast walk
(4-6 mph)?

(BTW, I gave the 30 lb. electric a brief trial and it was nice and
quiet but just didn't move that Guide V14 like it had that slick-
hulled Walker Bay 10.)

The Tohatsu has through-the-prop exhaust, compression release for easy
starting, and shallow water drive. It also comes standard with an oil
pressure indicator for low oil levels and a built-in 1.1 liter (.29
U.S. gallon) fuel tank as well as having the option to add an external
fuel tank. (It comes with the fittings.) It also has a forward-
neutral-reverse gearshift and a 123cc displacement motor with an RPM
range of 4500-5500 and a 59mm x 45mm bore and stroke. The gear ratio
is 2:15:1 and it weighs 57 lbs.

The dealer admits it's a 2007 but is brand-new in-the-box and never
been in the water. The $833 (delivered to my door) price is about
$150 cheaper than the price for a new 2008. It's even blue, same
color as our boat.

So has this rookie outboarder finally arrived at the best choice for
the boat and the projected uses? Hope so. The Tohatsu, compared to
the 5hp Briggs & Stratton (I had once given a fleeting glance to that
machine because of the low price) is 1hp and 15cc less but will
probably be easier on our ears while putting about and costs just a
very few dollars more than the Briggs. And finally, I just couldn't
see the Suzuki being worth $175-$200 more than the Tohatsu for our
needs.

So before I pick up that telephone and order in the next day or two,
any last minute observations, criticisms, etc. on what I hope to be
our final choice so we can quit agonizing over this outboard thing and
get out on the lake where we belong. Thanx again.

-Jay

+++The Tohatsu 4HP 4-Stroke

http://www.tohatsu.com/outboards/4_4st.html

+++Our G3 Guide V14 yacht

http://www.g3boats.com/AnglerVSeries/GuideV/#features

On Apr 15, 10:54 am, Martin Baxter wrote:

I'll bet that mostoutboardmanufactures measure output of just the
head, no shaft, no water pump.

Cheers
Marty

No, outboard power for all manufacturers has been measured at the
propshaft since the mid-1980s.

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