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Horse Power Qustion

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Does anyone know what the equivalent horse power is in an electric motor with a thrust of 50 lbs? Is there a general rule of thumb that so many lbs. of thrust = X horsepower?

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Keeler, thank you for the link.

 

After reading all the technical and intelectual verbage, my conclusion is those postulating, (A) they may not be able to translate their knowledge to us simple folk or, (B), they really don't have any practical experience. My question is for an approximate corolation between pounds of thrust to horsepower.

 

A call to a Minnkota dealer in my area revealed that they calculate approximtely 17 lbs of thrust is roughly about a horsepower.

 

How hard is that? :D

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A call to a Minnkota dealer in my area revealed that they calculate approximtely 17 lbs of thrust is roughly about a horsepower.

How hard is that? :D

 

Seriously doubt that will work. It's hard to compare "electric thrust" to "horsepower".

 

If the formula were true then a 65lb thrust electric would "theoretically" be 3.8hp.

 

When I was a kid I had a 12 alum that would plane out with a 3.5 gamefisher. There is NO way that boat would have planed with a 65lb electric.

That "formula" doesn't take into account max rpm, gearing and/or prop design.

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MdCrappie, I agree that 17 lbs = 1 hp is optimistic. It is doubtful that few if any electric motors can plane a boat, at least any I can afford. My intended use is for back trolling on a drift boat and to cut down my rowing time and get in more fishing time :D.

 

My question was asked to get a ballpark idea if any ratio might exist between Hp and Lbs of thrust. The only real way to test is to actually try it and see. I am hoping to do that in the next week or two.

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MdCrappie, I agree that 17 lbs = 1 hp is optimistic. It is doubtful that few if any electric motors can plane a boat, at least any I can afford. My intended use is for back trolling on a drift boat and to cut down my rowing time and get in more fishing time :D.

My question was asked to get a ballpark idea if any ratio might exist between Hp and Lbs of thrust. The only real way to test is to actually try it and see. I am hoping to do that in the next week or two.

 

Search youtube and you will see some "neat" little home built electric motors with will make small boats fly. Running like it has a 25hp gas on it.

 

To your situation for estimating the thrust you will need, a good rule is 1lb of thrust for each 100lbs of boat weight as a minimum in perfect conditions (no current and/or wind). Personally I would go with 2lb for each 100. I have a 16' alum and my 30lb moves it adequately in most conditions, but my 50lb thrust will put up a wake. I think it weighs about 1500lbs fully loaded.

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One horsepower is about 745 watts Watts = Volts X AMPS.

You are on a 12 volt system. If you have an ammeter on the electric motor, multiply the Amps by 12, which will give you the HP for that current. At 62 Amps you have 1 HP.

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Bill, the problem is that the wattage is not posted on my motor and websites specs do not list the wattage. I think 80% sounds optimistic too. What wattage is a 12 volt battery capable of running, approximately?

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Bill, the problem is that the wattage is not posted on my motor and websites specs do not list the wattage. I think 80% sounds optimistic too. What wattage is a 12 volt battery capable of running, approximately?

 

Most 12 volt trolling motors will draw about 1 amp per lb of thrust.

 

If you have a Group 27 battery they are generally about 105 a/h. This means that is will (theoretically) provide a total of 105 amps for 1 hour. So depending on your motor the run time will vary. If you have a 100lb thrust motor it should run just about 1 hour on top speed. If it were 50lb thrust it would run about 2 hours. If it is 17lbs of thrust it would run about 5 hours. Of course this is all based on a brand new 100% condition battery.

 

The easiest thing for you to do is tell us the following:

 

Size and approx weight of boat

Style of boat

What you want to electric motor to provide (ie positioning for fishing or running 5 miles down the lake)

 

 

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Thanks for the great info about battery life, was not sure what to expect.

 

I am hoping to use the electric back trolling, pulling Hot Shots, divers & bait, or back bouncing lead & bait. Backtrolling is done in a moving river, holding your boat in a stationary position by rowing, (think electric motor) and letting your line work in the river current below you. Periodically you allow your boat to slip downstream to cover new water.

 

I have an aluminum drift boat, kind of like a classic double ender Banks Dory but wider and the bottom is rockered to be very manuverable in swift water. It weighs about 300# empty, about 600>900# with two on board and gear. Generally you put in upstream and shutttle your truck and trailer to the take out downstream. Depending upon rainfall a river flow of about 1-1/2 > 3-1/2 mph is probably normal.

 

Now don't get me wrong, I enjoy rowing but many times two hands are not enough to manuever the boat and control a fishing rod. An electric might allow me to get a little more quality fishing time.

 

edsr

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