Re: [PSUBS-MAILIST] re-wiring trolling motors?

[Subscuba@aol.com]

This subject is a lot more interesting than Busby as long as we don't get 
into flame wars on whether MK or MG motors are better. 

I would prefer the MK motors without the motor controller built into the 
motor as the Motor Guide is reputed to do. I'm sure the cost of the motor and 
controller built as one unit is more expensive than separate units from a 
replacement viewpoint. Since I did my own controller, this made the most 
sense from a $ viewpoint. It would seem to me that having the controller 
built into the motor would offer much better cooling for the electronics but 
at the same time would expose the controller electronics to motor flooding. 
Better cooling of the electronics should equate for improved reliability for 
the MG electronics but at increased replacement cost and potentially lower 
reliability for flooding problems, even if they pot the electronics. I only 
paid $169 for my 70# thrust MK motor. So the MK electronics have less cooling 
but are separate units. Replacement of only the motor or controller makes 
sense to me.

Problems due to flooding or high moisture usually takes a long time to show 
up.

I do think that except for the placement of the controller and secondary 
considerations the two vendors are nearly equivalent. It's like discussing 
which is better, a Chevy or a Ford Pickup. They have to be able to do the 
same things, reliably and at nearly the same cost.

For reasons of stator demagnetization, most PM motors operating from 24 volts 
and up probably require controllers.

On the increase in speed for a 107 pound thrust versus a 101 pound thrust. 
Based on speed as a function of the cube root of horsepower (close enough at 
these speeds) the 107 pound thrust motor should give a higher speed by about 
1.9%. At a speed of about 5 knots this would increase the sub's speed by less 
than 0.09 knots, big difference. 

Ken Martindale 



In a message dated 11/26/00 10:08:45 AM Eastern Standard Time, 
caribsub@coqui.net writes:


> Other adavantage is the cost, less expensive since you don t need the upper
> unit, if you were interested I sale lower units MG 107 alone , forward and
> reverse, 36 / 24 Volts, plus the stainless steel shaft, plus the sacrificial
> anode to be mounted on the shaft and the prop kit for only $280, not
> including shipping via UPS or check with your motor dealer, but this
> solution is the most cost efficient.