DC Boat motor current [RE-wrenches]

[sunwise at cheqnet.net]

Wallace Stahle, Future Elec. Energy Co. wrote:
Would any of you have the formula for converting " Lbs of thrust" of a
given
> voltage DC motor boat motor into amps and/or speed, along the variables of weight,
> wind and water resistance that the boat provides?

I have a very small light-weight sail boat with a couple electric
trolling motors (no mast, instead I have a 75 watt siemens panle mounted
a a short PVC "mast" that charges the 110AH battery.  Both of my motors
came with info on how long a stanadard battery will power the motor at a
given power setting.  I think my 45 pound thrust draws about 25 amps at
12VDC (full power), but I can't remember is this is with the PV on line
and in the sun.  I can get 3 or 4 hours, especially with sun, but the
real benifit is that I just dock the boat after use and after a couple
days in the sun it's ready to go again.

HP has had a couple articles on electric boats and there are folks out
in Washington State that hold electric boat races.  I seem to remember
someone saying better thrust efficiency is accomplished by replacing the
prop with some kind of remote control model aircraft props.  

The Whaler has a planning hull and is a very heavy boat.  I wouldn't
imagine you'd get above walking speed with that motor but you might
approach it.  I've never played with a motor that size (130 LB thrust),
is it 24 volt?

Kurt Nelson

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