[PSUBS-MAILIST] Oil Compensation of Trolling Motors

[Subscuba@aol.com]

Hello,

Not to extend the pressure compensation versus existing seals, but I pressure 
compensate my Minn Kota trolling motor. I use a very simple, low cost SCUBA 
regulator and it works. Without intending to step on any toes, I agree with 
Pat on most of his comments. It's difficult not to get our ego's involved.

Oil compensation using the Trolling motors with brushes seems to me to be a 
bad idea because of the brush contamination. As stated by MK the motor will 
run after it has been flooded makes sense but it won't run without destroying 
the brushes after a short while. Your car battery will also work for a while 
in sea water. Humans will also operate for a while submerged in sea water. 
Think about the problems of making a rotating electrical contact to a 
segmented motor commutator. If enough oil got into the brushes it would break 
the electrical contact. In addition, the arcing in the brush to commutator 
area would decompose the oil and put a lot of gunk on the brushes. I don't 
recommend oil in motors with brushes although it would probably work for a 
while.

Best wishes,

Ken Martindale

The comments made by Steve and Vance which prompted me to comment are listed 
below.

In a message dated 10/6/00 2:23:03 PM Eastern Daylight Time, 
VBra676539@aol.com writes:

<< on them. I am making zero recommendations here, just suggesting that you 
not worry too much about it. Pick one and go with it.
 
 To extend the capabilities of the various trolling motors, it may be 
necessary to compensate. It's a simple deal, really. Drill two holes, thread 
for 1/4" pipe, screw in two plastic elbows, run a foot or so of soft walled 
tygon around the can, fill it full of oil and hit the water. (Wiring is the 
same either way. It ain't rocket science. Buy some bulkhead connectors and 
deal with it).
 
 Conversely, if you've got the drawings for one of Kittredge's units, chuck 
it up in the lathe, cut to spec, add paint, prop and sea water, in that order.
 
 Best Regards,
 Vance
  >>

>First, the Techs at MK tell me their seals will hold integrity for "about
>one additional atmosphere of pressure."  That says to me I should be able to
>dive my lower-end (motor) unit to about 33 feet (give-or-take) before she
>floods.  Now, even if she does flood, the motor will still continue to run:
>but the brushes will wear down at a much faster rate; so obviously I want to
>avoid that.