Conference wahoo::fishing

    I don't know much about the workings of electricity, but my guess
    is that a typical lamp dimmer switch would get real hot, then go pow! 
    from the current.

    Ed

    

    	I'd say give it a shot. About all you have to lose is the cost
    of a dimmer switch. 
    
    	RAYJ
    

    
    I don't think a dimmer switch would carry the current but a Automobile
    High/Low Beam switch could be rigged for foot control Hi Lo or Off
    On..............................
    
    
                                                  Steve

I'm afraid neither of the two preceding suggestions will work. Household lamp
dimmers are designed for alternating current - which you don't have on the boat.

Automotive dimmers are designed for 1 to 2 amp loads at most; all the lights
on your dashboard don't draw an amp. A trolling motor draws 6 to 30 amps. That's
why your trolling motor battery has to be beefy, and yet only lasts one day.

Your best hope is to pick up something like a Minn-Kota Maximizer. This is a 
box that you put between your battery and your trolling motor, which lets you
vary the motor speed. It's more than just a variable resistor; it actually
turns the motor on and off very rapidly. When it's off more than it's on, it
goes slow. On more than off, it goes fast. The important thing is, there's no
current being drawn when it's not needed, so your battery lasts longer. With
a variable resistor-type speed control, the unwanted current is turned into
heat and wasted.

These Maximizer-type speed controls do bad things to some boat electronics,
though, such as chart recorders. There's a discussion of this elsewhere in this
conference. In short, all that turning on and turning off can produce sharp
voltage rises (spikes or surges) that can get into a chart recorder and destroy
some transistors. Lowrance voids your guarantee if you have a maximizer on the 
boat.

If you don't have any fancy electronics on the boat, there's no cause for alarm.

Art

A headlight dimmer switch is more switch than dimmer. It selects which 
filament in the sealed beam (in dual beams) or which actual bulb (in a 4-light
vehicle) will be lighted. About the only application would be for a 
foot-operated on/off switch for a trolling motor.

I think Cabela's and Bass Pro Shop have trolling motor speed controls.

Art

    	Maybe you could make your own. If you take appart a slot car
    type controller you may be able to do a large scale duplication
    of it (pretty simple design). Other than that you may be able to get 
    something from an electrical supply house in the way of a variable
    D.C. motor control designed to handle the current. The author of
    .4 is most likely correct in that the current draw will burn out a 
    light dimmer. Other than that, I believe they both work on the 
    same principle (i.e. variable resistor). 
    	Another thought comes to mind when reading .4 is that the wires
    used to connect this should probably be the same size as those that
    run from the trolling motor to the battery.
        
    	RAYJ

    How about a fan switch?  They are made for a lot more current than
    a light dimmer.  They also work different.  The first speed is the
    fastest not the slowest.  This allows for a fan to get up to speed
    with all its power then a reduction can take place.
    
    Bob Puishys
    

    	After making the remark about trying the dimmer switch and having
    someone remind me aboutthe amount of current we're talking about, I figured
    I'd look around and see what I could find.
    
    	Note 286 in OVDAVX::ELECTRO_HOBBY has a discussion on D.C. motor 
    control. The author of the note was looking for basically the same info
    as the author of this note. 
    
    	I went back to look in the catalogs because I know I've seen
    variable speed electric trolling motors for a while but I don't
    recall seeing them with built in maximizers. I never noticed before 
    but it seems all of the motors with variable speed control today
    have some type of built in maximizer of sorts. They also have a
    significant increase in price (approx. $60+) over their 4-5 speed 
    counterparts.
    
    	I've always assumed that the 4-5 speed control on electric trolling
    motors used increasingly larger resistors to get slower speeds.
    Is this really the case ? If yes, where do they put the resistors?
    If they put them in the head I would expect it to get fairly hot and
    I don't recall it ever getting that hot. Do they put them under water
    with the motor to keep them cool ?
    
    	RAYJ

    re:10
    
    	Ray, 
    
    As I mentioned earlier there is a significant difference in the price
    of a trolling motor with the motor control vs. without. It would
    probably be just as cost effective to get the add-on maximizer or 
    a similar unit as an after market item then to try and incorporate
    it into an existing 4-5 speed motor.
    
    	RAYJ

    RE: The last few...
    
    The resistors in a Minn Kota are in the form a tapped coil located in
    the motor unit itself.  At full speed the coil is bypassed as it
    is when using a aftermarket Maximiser.  I would assume other brands
    are similar.
    
    As for using the Maximiser parts, the speed control module costs
    about $60.00, and the maintenance manuals don't give you a clue
    about the circuits involved.  I'm not even sure whether the $60.00 
    includes the required heat sink.  Add in a few support components, 
    and the price goes up.  As usual, buying the parts is many times
    more expensive than buying a complete unit.
     
    Unless you want to fool with untried designs and risk a unit that
    doesn't work well or at all, the best bet may be to try and pick
    up a used Maximiser, or sell your current moter and buy the one
    you really want.