Friday, May 31, 2013

Re: [Electric Boats] Trolling motors ==> electric outboards

 

Ya, I wish these people would cut the "#s of thrust" nonsense and
tell us the watts, or at least volts _and_ amps so we'd have some
idea and a basis for comparison. I think they want to hide it from us
so we don't realize how little power they have.

Craig

=====

>A trolling motor that produces, say 50# thrust at zero boat speed
>would produce zero thrust at 6 or 8 mph. Double the prop pitch and
>thrust at zero speed will drop while thrust at 8 mph will increase.
>Motor power is the same regardless.
>
>On Friday, May 31, 2013, danbollinger wrote:
>
>To a physicist, they are very different concepts. Thrust is a
>rotational unit of force. Power is a unit of work.
>
>Energy / Time = Power

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Re: [Electric Boats] Outboard conversions...

 

>Do we have many documented conversions in the group?

The Honda 7.5 HP with my Electric Caik motor/Turquoise BLDC motor
controller worked nicely in February. Youtube - 3 short, low-rez
clips:
http://youtu.be/zrtE6yHSFRw - rundown of the setup
http://youtu.be/jen-WpfaM4k - pulling out
http://youtu.be/-L3yHhgoFmE - a bit more footage
See also my newsletters, esp. covering February. (Dec, Jan, covered
making the motor.)

I connected the motor straight to the shaft going down the leg with a
flex/joy coupling. Quiet, simple.

The main objection is the 2.7(?)-to-one prop speed reduction down in
the foot, limiting the prop RPM and the speed even on a small boat.
The greater torque of an electric motor goes to waste and (generally)
it doesn't reach the high RPMs of gas. I think this has been noted
before on this list as being a common problem for doing electric
conversions of gas outboards. I've seen a chain drive used to speed
up the drive shaft to compensate, with an 8 HP Mars motor. (In fact,
here's his video... http://www.youtube.com/watch?v=BP7LMbqV8Lc .)
Belt(s) would be quieter.

Craig

http://www.TurquoiseEnergy.com/
http://www.saers.com/recorder/craig/TENewsV2/ - newsletters

Victoria BC

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Re: [Electric Boats] Trolling motors ==> electric outboards

 



My ketch has a Norwegian Sabb (not Saab) Model G 10hp diesel that features a controllable-pitch 18" 2 blade prop. It's simple and reliable. The shaft moves longitudinally to change the pitch. The pitch is continuously variable from full reverse to full forward. They also offered a fully feathering version of this prop.

Sorry, it's no longer available. Sabb made this engine from 1948-2001, and I wish I had one in a crate for some future build. You do sometimes see these engines for sale used, including their prop and shaft. Maybe there's a dead one out there for sale cheap that has a good prop...

-Tom

--- In electricboats@yahoogroups.com, Kirk McLoren <kirkmcloren@...> wrote:
>
>
>
>  I remember taking a ride in a Cessna 180. That variable pitch prop made a huge difference.
> Prop failure in a boat isn't as catastrophic as an airplane so why don't we see them?
>
>
>
>
>
>
> ________________________________
> From: Dennis Wolfe <wolfeboats@...>
> To: "electricboats@yahoogroups.com" <electricboats@yahoogroups.com>
> Sent: Friday, May 31, 2013 5:19 PM
> Subject: Re: [Electric Boats] Trolling motors ==> electric outboards
>
>
>
>  
> A trolling motor that produces, say 50# thrust at zero boat speed would produce zero thrust at 6 or 8 mph. Double the prop pitch and thrust at zero speed will drop while thrust at 8 mph will increase. Motor power is the same regardless. 
>
> On Friday, May 31, 2013, danbollinger wrote:
>
>
> > 
> >To a physicist, they are very different concepts. Thrust is a rotational unit of force. Power is a unit of work.
> >
> >Energy / Time = Power
> >
> >--- In electricboats@yahoogroups.com, John Francis <surv69@> wrote:
> >>
> >> I don't understand how someone can say THRUST is not power, since the
> >> THRUST that an engine, along with gearing and a propeller, is the wash that
> >> is produced as yourr boat moves forward . . . and of course, what we're all
> >> looking for is to move our boats forward.
> >>
> >>
> >>
> >> On Thu, May 30, 2013 at 10:48 PM, John Riehl <riehlj2002@> wrote:
> >>
> >> >
> >> >
> >> > By contrast, I attempted to use a 36 lb thrust MinnKota on a 1,800 lb 22'
> >> > MacGregor. It would move the boat, but couldn't push it against anything
> >> > more than about 10 kts of wind.
> >> >
> >> > *From:* Skip von Niederinghausen <farharbour@>
> >> > *To:* electricboats@yahoogroups.com
> >> > *Sent:* Thursday, May 30, 2013 6:49 AM
> >> >
> >> > *Subject:* [Electric Boats] Re: Trolling motors ==> electric outboards
> >> > **
> >> >
> >> > Maybe I should mention to the group that years ago, I used a Min Kota
> >> > 24lb thrust trolling motor on my International Folkboat which was 26'
> >> > LOA and displaced about 5000lbs. This was in Annapolis Maryland where
> >> > there is little tide or currents. The motor was great for getting off the
> >> > dock at my house, then under the Eastport Bridge and out into the bay. I
> >> > used her for only overnight trips in the area and this system worked fine
> >> > for this limited use.** **Skip**
> >> > **-- **"The sky hides the night behind it and shelters the people beneath
> >> > from the horror that lies above."** -- Paul Bowles<http://www.goodreads.com/author/show/7659.Paul_Bowles>
> >> > ****
> >> >
> >> >
> >> >
> >> >
> >> >
> >>
> >
> >
>

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Re: [Electric Boats] Trolling motors ==> electric outboards

 

On 01/06/13 12:59, Kirk McLoren wrote:
>
>
>
> I remember taking a ride in a Cessna 180. That variable pitch prop
> made a huge difference.
> Prop failure in a boat isn't as catastrophic as an airplane so why
> don't we see them?
>
>
You do sometimes. A friend's brother-in-law worked on a variable-pitch
system for an outboard. The customer was apparently military - landing
boats. They wanted the absolute most out of their motors in all
conditions. And cost wasn't an issue.

Sydney's Manly ferry's use variable-pitch props, one at each end. But
they are a 1140 ton 70m long commuter ferry.

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Re: [Electric Boats] Trolling motors ==> electric outboards

 


 I remember taking a ride in a Cessna 180. That variable pitch prop made a huge difference.
Prop failure in a boat isn't as catastrophic as an airplane so why don't we see them?





From: Dennis Wolfe <wolfeboats@gmail.com>
To: "electricboats@yahoogroups.com" <electricboats@yahoogroups.com>
Sent: Friday, May 31, 2013 5:19 PM
Subject: Re: [Electric Boats] Trolling motors ==> electric outboards

 
A trolling motor that produces, say 50# thrust at zero boat speed would produce zero thrust at 6 or 8 mph. Double the prop pitch and thrust at zero speed will drop while thrust at 8 mph will increase. Motor power is the same regardless. 

On Friday, May 31, 2013, danbollinger wrote:
 
To a physicist, they are very different concepts. Thrust is a rotational unit of force. Power is a unit of work.

Energy / Time = Power

--- In electricboats@yahoogroups.com, John Francis <surv69@...> wrote:
>
> I don't understand how someone can say THRUST is not power, since the
> THRUST that an engine, along with gearing and a propeller, is the wash that
> is produced as yourr boat moves forward . . . and of course, what we're all
> looking for is to move our boats forward.
>
>
>
> On Thu, May 30, 2013 at 10:48 PM, John Riehl <riehlj2002@...> wrote:
>
> >
> >
> > By contrast, I attempted to use a 36 lb thrust MinnKota on a 1,800 lb 22'
> > MacGregor. It would move the boat, but couldn't push it against anything
> > more than about 10 kts of wind.
> >
> > *From:* Skip von Niederinghausen <farharbour@...>
> > *To:* electricboats@yahoogroups.com
> > *Sent:* Thursday, May 30, 2013 6:49 AM
> >
> > *Subject:* [Electric Boats] Re: Trolling motors ==> electric outboards
> > **
> >
> > Maybe I should mention to the group that years ago, I used a Min Kota
> > 24lb thrust trolling motor on my International Folkboat which was 26'
> > LOA and displaced about 5000lbs. This was in Annapolis Maryland where
> > there is little tide or currents. The motor was great for getting off the
> > dock at my house, then under the Eastport Bridge and out into the bay. I
> > used her for only overnight trips in the area and this system worked fine
> > for this limited use.** **Skip**
> > **-- **"The sky hides the night behind it and shelters the people beneath
> > from the horror that lies above."** -- Paul Bowles<http://www.goodreads.com/author/show/7659.Paul_Bowles>
> > ****
> >
> >
> >
> >
> >
>



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Re: [Electric Boats] Trolling motors ==> electric outboards

 

A trolling motor that produces, say 50# thrust at zero boat speed would produce zero thrust at 6 or 8 mph. Double the prop pitch and thrust at zero speed will drop while thrust at 8 mph will increase. Motor power is the same regardless. 

On Friday, May 31, 2013, danbollinger wrote:

 

To a physicist, they are very different concepts. Thrust is a rotational unit of force. Power is a unit of work.

Energy / Time = Power

--- In electricboats@yahoogroups.com, John Francis <surv69@...> wrote:
>
> I don't understand how someone can say THRUST is not power, since the
> THRUST that an engine, along with gearing and a propeller, is the wash that
> is produced as yourr boat moves forward . . . and of course, what we're all
> looking for is to move our boats forward.
>
>
>
> On Thu, May 30, 2013 at 10:48 PM, John Riehl <riehlj2002@...> wrote:
>
> >
> >
> > By contrast, I attempted to use a 36 lb thrust MinnKota on a 1,800 lb 22'
> > MacGregor. It would move the boat, but couldn't push it against anything
> > more than about 10 kts of wind.
> >
> > *From:* Skip von Niederinghausen <farharbour@...>
> > *To:* electricboats@yahoogroups.com
> > *Sent:* Thursday, May 30, 2013 6:49 AM
> >
> > *Subject:* [Electric Boats] Re: Trolling motors ==> electric outboards
> > **
> >
> > Maybe I should mention to the group that years ago, I used a Min Kota
> > 24lb thrust trolling motor on my International Folkboat which was 26'
> > LOA and displaced about 5000lbs. This was in Annapolis Maryland where
> > there is little tide or currents. The motor was great for getting off the
> > dock at my house, then under the Eastport Bridge and out into the bay. I
> > used her for only overnight trips in the area and this system worked fine
> > for this limited use.** **Skip**
> > **-- **"The sky hides the night behind it and shelters the people beneath
> > from the horror that lies above."** -- Paul Bowles<http://www.goodreads.com/author/show/7659.Paul_Bowles>
> > ****
> >
> >
> >
> >
> >
>

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[Electric Boats] Re: Trolling motors ==> electric outboards

 

To a physicist, they are very different concepts. Thrust is a rotational unit of force. Power is a unit of work.

Energy / Time = Power

--- In electricboats@yahoogroups.com, John Francis <surv69@...> wrote:
>
> I don't understand how someone can say THRUST is not power, since the
> THRUST that an engine, along with gearing and a propeller, is the wash that
> is produced as yourr boat moves forward . . . and of course, what we're all
> looking for is to move our boats forward.
>
>
>
> On Thu, May 30, 2013 at 10:48 PM, John Riehl <riehlj2002@...> wrote:
>
> >
> >
> > By contrast, I attempted to use a 36 lb thrust MinnKota on a 1,800 lb 22'
> > MacGregor. It would move the boat, but couldn't push it against anything
> > more than about 10 kts of wind.
> >
> > *From:* Skip von Niederinghausen <farharbour@...>
> > *To:* electricboats@yahoogroups.com
> > *Sent:* Thursday, May 30, 2013 6:49 AM
> >
> > *Subject:* [Electric Boats] Re: Trolling motors ==> electric outboards
> > **
> >
> > Maybe I should mention to the group that years ago, I used a Min Kota
> > 24lb thrust trolling motor on my International Folkboat which was 26'
> > LOA and displaced about 5000lbs. This was in Annapolis Maryland where
> > there is little tide or currents. The motor was great for getting off the
> > dock at my house, then under the Eastport Bridge and out into the bay. I
> > used her for only overnight trips in the area and this system worked fine
> > for this limited use.** **Skip**
> > **-- **"The sky hides the night behind it and shelters the people beneath
> > from the horror that lies above."** -- Paul Bowles<http://www.goodreads.com/author/show/7659.Paul_Bowles>
> > ****
> >
> >
> >
> >
> >
>

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Re: [Electric Boats] The cost of going electric

 

My experience is very similar to Eric's. When I pulled out the diesel and converted to electric propulsion six years ago  it was about a wash cost wise with a new diesel. Perhaps a little less. Where I have saved and continue to save is in maintenance costs and costs of my time. This is because my electric propulsion system requires very little maintenance.  No oil, anti freeze, zinc changes. No winterizing. Having an AGM battery bank also helps over flooded batteries as would Lithium batteries. The AGM bank has been working well as I begin my sixth season with EP. There are additional savings in that I can also use my propulsion bank to help supply additional energy when at anchor. For example when I use my laptop I often use a 48 to 12 volt converter to power it off the EP bank. Since the 48 volt battery bank is just sitting there I don't have to worry about draining down the 12 volt house battery bank. I let it continue to power my refrigeration system, lights and other essential boat needs. The 48 volt then gets recharged with my wind turbine and solar panels rather quickly. So I have not felt the need to increase the house battery bank size. Also most of the time I never have to fire up the Honda 2000 generator except after a day of cruising where I had to use some additional EP. In short my experience is the savings add up in the operating costs of an EP system not necessarily in the installation. But, I think a lot of people don't consider that when they are trying to decide if EP is the way to go.

Capt Mike
http://biankablog.blogspot.com
 

From: Bud Elkin <bud.elkin@gmail.com>
To: electricboats@yahoogroups.com
Sent: Friday, May 31, 2013 8:22 AM
Subject: Re: [Electric Boats] The cost of going electric

 
Eric,
Great summation!!! I went solar for several reasons: one, I had the room on top of my houseboat to hold plenty of solar panels(6)-280wh, two, I got the solar panels for around $210 a piece, and 12 deep cycle batteries for $50 a piece. I built my outboard motor from an old 1965 Evinrude with a A00 4009 DC motor that I had laying around. Powering or re-powering a boat is expensive whether buying sails or motors; no argument.

bud..


On Thu, May 30, 2013 at 7:45 PM, Eric <ewdysar@yahoo.com> wrote:
 
Hi John,

While I understand the pocketbook perspective, there isn't a really good way around it. I had the same problem when I realized that my Catalina 22 needed new sails, they cost more than I had spent on the entire boat. I guess that I could have made my own from Tyvek and duct tape (anybody trying to drive their boat with a 500W blender motor?), but let's be real. I once had a truck where new tires cost more than the truck was worth, but I still needed tires.

I have notived that many people end up here because their boat needs a new engine, a new gas or diesel engine is expensive and they figure that why not go electric, it must be cheaper, right?

I'm not sure why anyone would think that, because it's not true in any other electric vs. gas product. Let's look at a couple of gasoline and battery powered products. Don't get distracted by corded appliances, your boat would need a reallllly long cord.

Cordless electric mower = $300 - $400
Similar gas powered mower = $150 - $300

Electric standup scooter = $500 - $1200 (not the toy versions)
Similar gas powered scooter = $400 - $1000

Electric Nissan Leaf = $28,000
Similar Nissan Versa = $15,000

For each of these, the gas version is typically faster, more powerful and has much greater range.

So why do we think that a repower with electric should be less expensive than a new gas or diesel engine?

In my case, the electric repower installed by me cost almost exactly the same as if I had installed a new diesel engine myself. For me,it was well worth it, for another boater, it might be a horrible idea. In fact, after converting my 30' ketch to electric, I had to replace the outboard on my 27' trimaran. I wanted to go electric, but a new outboard was much lighter, more powerful, cheaper, easier, easily sourced, had the range required by offshore racing regulations, etc. etc. The trimaran got a new 4 stroke outboard, and I'm already a strong supporter of electric conversions.

Honestly, did anybody here get into boating because it is so inexpensive? Sure, many of us operate right at the edge of our ability to spend, me included. I never want to spend more than I have to, but sometimes trying to save money can cost me more in the long run. And my personal safety is priceless....

Electric is just another drive option, it is not a universal panacea. Installed for the right reasons in the right use case, they are brilliant. Otherwise, they can be too much of a compromise.

Just something to think about....

Eric
Marina del Rey, CA

PS. Yes, I had a friend that made sails for a Chrysler 23 from Tyvek and duct tape, and they worked.... kind of. IMHO, the money that I've spent on sails (and my electric conversion) has been well worth it.

--- In electricboats@yahoogroups.com, oak <oak_box@...> wrote:
>
> Eric,
>  
> While I can "intellectually" appreciate the wisdom of all that you're saying, my pocketbook doesn't want to hear it...   <grin>
>  
> Seriously, I get what you're saying, and it makes a lot of sense.
> You make a good point about the sizing of the props on the trolling motors.  I can tell you that the prop on my Torqeedo 4R is BIG compared to any trolling motor, and definitely even any kind of outboard up to the same size.  If you believe the Torqeedo literature, they specifically designed the prop on that motor for the electric outboard application, and it seems to do a good job (though I'm anxious to get more experience with it).
>  
> This afternoon, I came across the Minn-Kota Riptide that has dual motor units and is rated at 160 pounds thrust - close to what the Torqeedo 4R is, and at 24V (I didn't see anything that listed how many amps it would draw).
>  
> At 1/2 to 1/3 the price - it's very appealing.
> But again, your points about prop size, motor speed, etc, are all well taken.
>  
> I happen to already have the Torqeedo 4R that I will experiment with on the C-22.  But if I could afford to get down to a 24V system instead of a 48V system, it becomes much more reasonable to get a single 24V lithium pack than to have to buy two.  If only money weren't an object.
>  
> The unfortunate reality there is that I can easily spend 3x the price of the boat on the outboard and batteries!
> So yes, there are tradeoffs to be made.  And fortunately - in MY case - I don't have to go terribly far on battery power.   It would be really nice to be able to cruise 2-3 hours.   Typical case (at least if I was sailing) would probably be 30 min. to less than an hour, and a good amount of that could be at reasonably low power.
>  
> I really wish I had the spare disposible cash to buy one of each of several and try them all out!   If the 80 foot pound motor was enough to push the boat around a little bit, it would be fun to have the Torqeedo 2.0 as the main engine, and the trolling motor in a locker as a backup.  Then it would be fun to have the 24V lithium as the main battery, probably with two cheap FLA batteries as a standby bank that I knew would get me at least 30-60 min at low speed to get me home if I exhausted the primary bank...
>  
> I need to buy more lottery tickets...
>  
> John
> (aka "oak_box", but not really - just John.)
>
>




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Re: [Electric Boats] The cost of going electric

 

Eric,
Great summation!!! I went solar for several reasons: one, I had the room on top of my houseboat to hold plenty of solar panels(6)-280wh, two, I got the solar panels for around $210 a piece, and 12 deep cycle batteries for $50 a piece. I built my outboard motor from an old 1965 Evinrude with a A00 4009 DC motor that I had laying around. Powering or re-powering a boat is expensive whether buying sails or motors; no argument.

bud..


On Thu, May 30, 2013 at 7:45 PM, Eric <ewdysar@yahoo.com> wrote:
 

Hi John,

While I understand the pocketbook perspective, there isn't a really good way around it. I had the same problem when I realized that my Catalina 22 needed new sails, they cost more than I had spent on the entire boat. I guess that I could have made my own from Tyvek and duct tape (anybody trying to drive their boat with a 500W blender motor?), but let's be real. I once had a truck where new tires cost more than the truck was worth, but I still needed tires.

I have notived that many people end up here because their boat needs a new engine, a new gas or diesel engine is expensive and they figure that why not go electric, it must be cheaper, right?

I'm not sure why anyone would think that, because it's not true in any other electric vs. gas product. Let's look at a couple of gasoline and battery powered products. Don't get distracted by corded appliances, your boat would need a reallllly long cord.

Cordless electric mower = $300 - $400
Similar gas powered mower = $150 - $300

Electric standup scooter = $500 - $1200 (not the toy versions)
Similar gas powered scooter = $400 - $1000

Electric Nissan Leaf = $28,000
Similar Nissan Versa = $15,000

For each of these, the gas version is typically faster, more powerful and has much greater range.

So why do we think that a repower with electric should be less expensive than a new gas or diesel engine?

In my case, the electric repower installed by me cost almost exactly the same as if I had installed a new diesel engine myself. For me,it was well worth it, for another boater, it might be a horrible idea. In fact, after converting my 30' ketch to electric, I had to replace the outboard on my 27' trimaran. I wanted to go electric, but a new outboard was much lighter, more powerful, cheaper, easier, easily sourced, had the range required by offshore racing regulations, etc. etc. The trimaran got a new 4 stroke outboard, and I'm already a strong supporter of electric conversions.

Honestly, did anybody here get into boating because it is so inexpensive? Sure, many of us operate right at the edge of our ability to spend, me included. I never want to spend more than I have to, but sometimes trying to save money can cost me more in the long run. And my personal safety is priceless....

Electric is just another drive option, it is not a universal panacea. Installed for the right reasons in the right use case, they are brilliant. Otherwise, they can be too much of a compromise.

Just something to think about....

Eric
Marina del Rey, CA

PS. Yes, I had a friend that made sails for a Chrysler 23 from Tyvek and duct tape, and they worked.... kind of. IMHO, the money that I've spent on sails (and my electric conversion) has been well worth it.

--- In electricboats@yahoogroups.com, oak <oak_box@...> wrote:
>
> Eric,
>  
> While I can "intellectually" appreciate the wisdom of all that you're saying, my pocketbook doesn't want to hear it...   <grin>
>  
> Seriously, I get what you're saying, and it makes a lot of sense.
> You make a good point about the sizing of the props on the trolling motors.  I can tell you that the prop on my Torqeedo 4R is BIG compared to any trolling motor, and definitely even any kind of outboard up to the same size.  If you believe the Torqeedo literature, they specifically designed the prop on that motor for the electric outboard application, and it seems to do a good job (though I'm anxious to get more experience with it).
>  
> This afternoon, I came across the Minn-Kota Riptide that has dual motor units and is rated at 160 pounds thrust - close to what the Torqeedo 4R is, and at 24V (I didn't see anything that listed how many amps it would draw).
>  
> At 1/2 to 1/3 the price - it's very appealing.
> But again, your points about prop size, motor speed, etc, are all well taken.
>  
> I happen to already have the Torqeedo 4R that I will experiment with on the C-22.  But if I could afford to get down to a 24V system instead of a 48V system, it becomes much more reasonable to get a single 24V lithium pack than to have to buy two.  If only money weren't an object.
>  
> The unfortunate reality there is that I can easily spend 3x the price of the boat on the outboard and batteries!
> So yes, there are tradeoffs to be made.  And fortunately - in MY case - I don't have to go terribly far on battery power.   It would be really nice to be able to cruise 2-3 hours.   Typical case (at least if I was sailing) would probably be 30 min. to less than an hour, and a good amount of that could be at reasonably low power.
>  
> I really wish I had the spare disposible cash to buy one of each of several and try them all out!   If the 80 foot pound motor was enough to push the boat around a little bit, it would be fun to have the Torqeedo 2.0 as the main engine, and the trolling motor in a locker as a backup.  Then it would be fun to have the 24V lithium as the main battery, probably with two cheap FLA batteries as a standby bank that I knew would get me at least 30-60 min at low speed to get me home if I exhausted the primary bank...
>  
> I need to buy more lottery tickets...
>  
> John
> (aka "oak_box", but not really - just John.)
>
>


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Re: [Electric Boats] Re: Trolling motors ==> electric outboards

 

General Thrust Equation:    http://www.grc.nasa.gov/WWW/k-12/airplane/thrsteq.html
Since thrust is dependent on the mass, velocity, and density, it would be difficult to put a thrust figure on a motor.

Horsepower:    http://en.wikipedia.org/wiki/Horsepower#Nominal_horsepower
 When you change the pitch or diameter of a propeller, you change the amount of water pushed to the rear per rotation of the shaft. The pitch and size of the prop are matched to the speed that you want the greatest thrust. IC engines have low torque at low speeds and operate best at high speeds. Electric motors have high torque at low speeds.

IC engines are generally rated at brake horspower  (power off the crankshaft). Electric motors are rated off the shaft. Since the Torqeedo mounts the prop right off the motr shaft, there are no losses due to friction, acessories, or drivetrain losses.

1 hp = 746 watts = .746 kw
 
Joe Murray
Different Drummer #364
Panama City, FL
From: John Francis <surv69@gmail.com>
To: electricboats@yahoogroups.com
Sent: Thursday, May 30, 2013 1:05 PM
Subject: Re: [Electric Boats] Re: Trolling motors ==> electric outboards

 
I'm going to go out on a limb and pretend I think I know what I'm talking about, simply becuase the thrust and HP is too confusing.
 
It appears to me that electric motors, while having a HP rating(of the actual motor), in a boat propulsion system ... is rated in thrust.
 
Evidently THRUST already computes all the prop data and revolutions to achieve a specific THRUST ... like a packaged, computed value.
 
I've heard that if a person changes over a MinnKota prop to a Kipawa-type prop, the THRUST increases, while the motor in the buld unit remains the same.
 
So THRUST is the value of pushing power off of the propeller and whatever speed is predetermined as the base-speed(motor).
 
A 10 HP I.C., is an engine that delivers 10HP of work at some point between the cylinders and the propeller shaft.  You can put a double sized prop with a double deep bite, and the motor remains a 10HP motor. If you put a smaller prop on a 10HP motor, it remains a 10HP motor.
 
So many variations that all come down to pairing up different components.
 
Personally, I think THUST is the most descriptive value of what the motor can do for us.
 
This is not that electric mootors need to have available HP ratings, but rather, that IC engines should be computed for THRUST ratings.  After all it is THRUST that pushes water astern of you boat.
 
Probably, none of this is important . . . bigger is better . . . until a group of "green", sailors with displacement hull sailboats, who work in that magic marginal land of decifering THRUST, HP, matching propellers, prop speed and torque.
 






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