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Old 16-12-2008, 17:35   #1
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Minikota how much thrust do I really need?

Hey so I'm curious. I have a 21 foot sail boat, fixed keel, and I am wondering if one of those little minikota trolling motors would get me in and out of the marina any easier or if it would just be an expensive transom ornament? If it would work whats the minimum amount of thrust i could use?
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Old 16-12-2008, 22:52   #2
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Just a little more info needed. How far do you have to go to get under sail? What are the water conditions - i.e. rough or smooth. I presume you are lake sailing?

I looked at those motors. The 55 model is the only 12 volt. I reckon in benign conditions it will easily move your boat of and on the dock.

The temptation will be to try and use it for "go home" propulsion when the wind dies. I don't think it is suitable for that. maybe the 24V or 36V models are but then you are talking more battery power needed.

How do you charge? Is there shorepower nearby?

I'd certainly consider it if I were you but I would also look at a small gas engine first.

Overall it may be less hassle.
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Old 17-12-2008, 03:36   #3
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See the excellent on-line article:
Electric Trolling Motors for Auxiliary Propulsion on Sailboats
by Charles Brennan and Jobst Vandrey

Electric Trolling Motors for Auxilliary Propulsion on Sailboats

This Mariner 24 Sailboat claims to get a maximum forward speed of 4.7 mph with a 107 lbs. thrust Electric Trolling Motor (MotorGuide ET107V):
Electric Drive for Sailboats

Trolling Motor Thrust and Outboard Horsepower cannot be directly compared.

Estimating H.P. equivalent of Electric Trolling Motor:
Horsepower = [(Battery Voltage x Current Draw) x o/all efficiency] 750*
For electric outboards, overall efficiencies range between 20% for trolling motors and up to 35% for larger electric propulsion motors.

* 1 H.P. = 746 Watts (I used 750W for simplicity)
The electrical horsepower, as used by the electrical industry for electrical machines, is defined to be exactly 746 W at 100% efficiency. Electric motors can never run at 100% efficiency. Overall efficiency is motor efficiency x drive efficiency.
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Old 17-12-2008, 08:37   #4
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cool

great thanks guys. thats all i really needed to know
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Old 17-12-2008, 10:44   #5
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Hey Jon,

I use a Minnkota 55lb. thrust on my 17' sailboat. No fixed keel though. We move along at about 3knts. The nice thing is that it is whisper quiet and there is no odor. We replaced a 1968 Johnson 2hp 2 cycle...

The bad news is that in some rough conditions that we ran into late in the season it could barely push us where we needed to go (to windward). The chop and wind were too much for the little guy.

Overall for us it has been fine though, the farthest we motored was about 4 miles one day when the wind completely dropped off on the lake. Usually we just use it to get away from the launch and back in.

But, like I said to start our boat is smaller and lighter. Good luck!
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Old 17-12-2008, 13:37   #6
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Our club uses a 27lb thrust Minn Kota to move a 19 foot WWP (1500lb) boat on and off its mooring when the wind dies and there is a bit of a current. A solar panel charges the battery on its mooring. I've used the Minn Kota for 2 miles and up a small river on the same boat. It will not get you to windward if you have rigging failure in a 10 knot wind.
Hope this helps.
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