View Full Version : Worth fixing older Motor guide unit?

old dog new tricks
06-12-2020, 03:08 PM
New to forum. I have a Motor Guide unit with partial ID information that does not run properly.
It has no proper ID information (Manufacturers decal/plate with serial/model etc) but Motor head graphics and observation provide the following: GWF 35; 12V; 41 # Thrust; 1995 Brunswick; Whisper Guide; Great White Series; On the underside of the head is a 1/4" by about 2" label with the print of: "FLY21250". The same sticker/label in found on the inside of the head cover. It is a bow mount with foot pedal which contains a 3 position toggle switch (with 3 lugs on the back), a rotary pot (with three lugs on the back) and a momentary on/off foot switch opposite the rotary speed dial.

Observations so far when unit is connected to battery; Initially slight "click" of a relay in the head; then three position switch in upper (closest to toe) position - nothing when momentary switch is activated - turning foot mounted the speed dial still nothing. Switch in center position same results. Switch in Heel (closest to heel) position motor runs at full speed regardless of position of foot controlled speed dial/pot.

Not sure which combination of lugs to test on an Ohm/volt meter on the pot and the 3 position switch or what readings I should be getting.
Trying to determine if he unit is worth fixing up or not (probably for sale since my 14' jon boat doesn't need a bow mount motor with a 30" mount bracket :o).

Any help/direction appreciated.

old dog new tricks
06-14-2020, 02:39 PM
Old Dog here again - additional information.
Tested 3 pos switch using center lug as the common. Upper and lower positions go "off and on toggling the switch. Assume switch is OK. Momentary switch tests out OK. Speed pot again using the center lug (red wire) as the common, the top lug (black wire) shows 0 Ohms max clockwise and 27.1 Ohms max counter clockwise. Bottom lug (green wire) shows just the opposite - 0 Ohms max counter clockwise, and 27.1 Ohms when the pot is turned to max clockwise. Ohm meter is set at 200K Ohms position, and All three lugs are not connected to anything eliminating possible errant reading due to down line resistances of other parts of the circuit. Given these results, I am assuming all three components operate as designed (the Pot, the 3-way and the momentary switch).

In the head there is a circuit board with a relay and other components, capacitors, resisters etc, the part number seems to be JF 157-03. Wondering if this is possibly the "bad part" or if something in the wiring or the motor is faulty.

This unit may have been sold/serviced by Sears. Mercury parts/history don't seem to recognize this model but I found one reference by Sears where they did recognize this specific model number (GWF 35).

Any direction or advice would be appreciated or pricing on a JF 157-03 board.