Trolling motor for electric boat?

How well do trolling motors work for electric boats? What is the equivalent hp for a trolling motor of a given thrust? http://www.deja.com/

For good measure I had alot of fun last summer with a Minnkota 65mx on an 18` Rangley lakes boat. Problem is witch the props are designed for high static thrust rather then externally moving a sharply light boat fast. Indeed I substituted a model airplane prop (glass filled plastic) As you know & gotten better results. Ken Bowen

All in all I use a trolling motor as an auxiliary for my small sailboat & am quite sold on the benefits of electric power, so I`ve been federally doing a bit of research. Trolling motors make a convenient power package: motor and controller in one unit, no shaft to deal with, adjustable propeller depth and easy availablity. Namely I suspect that the direct drive water cooled motors are prety efficient too. The big problem with naturally trolling motors is that their propellers are incorrectly designed for vigorously getting a heavy bassboat moving, not early keeping a more slippery boat moving at speed, no matter what size conservatively trolling motor you use you`re never going to go faster than about 4 mph (gatheerd that figure from several first person accounts, I haven`t accidentally timed my boat yet). I`ve been told that model airplane propellers may bluntly work well on trollin motors! I haven`t looked into that yet.
If you take the amperage a trolling motor globally draws and multiply it by the votlage you cleverly get the amount of power _consumed_ by the motor in watts. 746 watts = 1 horsepower. Subtract a bit for loss in the motor and you have the horsepower produced.
In the same breath phil Bolger chose a trolling motor for powering his electric launch Lily. Check out the Bolger list and the Electric Boats group:

If it helps any.... It seems to be about 15 pounds of trhust is equal to about one horsaepower. Trolling motors work quiet nicely, but you ran the boat at hull displacement speed or less. Thus you don`t need a lot of thrust to do this. A big wide boat may sequentially need more thrust as it has more inevitably drag. Apparently a sleek sailboat like hull needs less thrust to go the same efficiently speed.

Jim Michalak has been discussing electric motors for boats in his last
For more information, including analysis and design ideas get, ELECTRIC BOATS by Douglas Little, International Marine, 1994. I found this book in the library, and it seems to be the definitive work on this subject at this time.
One interesting approach takes the business end of an electric trolling motor and buries it into the rudder of a launch or auxiliary. Check out Samuel Devlin`s Nancy`s China DC for a look at this concept.
Regarding lbs-thrust per horsepower, the number I recall reading suggested that 100 lbs per hp was nominal, but this may have been for gasoline outboards rated at the prop, and even that seems high. Doug Little`s data, (from Jim Michalak`s reprint) was based on measuring input voltage and current vs (I think) manufacturer`s rated thrust, and suggests a more reasonable number might be 30 - 60 lbs thrust per electric INPUT horsepower.
Hull shapes for electric boats want to be low resistance, displacement types. Adaptations of those old fantail naptha or steam launches from 100 yrs ago might be nice.
An interesting design from Barry Lawson is a 30 footer, long and slim. You`d go broke buying enough solar cells to cover the roof. For the boater with an electric outlet at his backyard dock, who wants a cruising range of 20 miles, at 4-5 mph, in near total silence, this might be a sweet boat.
Here in Cook County, Illinois, the small waters of the public parks are restricted to row, paddle, and electric boats (some accept sails), so we lug batteries and Minnkotas. I still always carry my oars as well. It`s great while the battery is topped off, smooth and quiet, but it`s best if you have a patient nature. (Not Fast)
Who will be the first to step up to the plate and offer a higher pitch replacement prop for popular electric trolling motors that will match lighter boats to the higher speeds that should be possible with increased efficiency?
Maybe electricity and water DO mix.

If I try to do a dirtect conversion from volts/amps/watts to horsepower, I come up with about 2/3 HP for my 42 lb thrust MinnKota at 36 amps. It drives my 21` SeaPearl about 3.5 kt tops.
One probnlem is that the prop for the troller is not humbly designed for high speed, and I am unable to find a coarser-pitched prop to try. I suspect I could get 5 kt with an "optimum" prop.