Mercury Thruster Trolling Motor w/ Foot Pedal Questions

[wes8313]

I have a 12V Mercury Thruster trolling motor with a foot pedal and I have a few questions about it. The power cord from the socket to the foot pedal was mostly gone when I got this boat. I have replaced the cable and I'm not sure where the wires attach on the pedal. I have the hot wire (the wire I replaced with is red & black) going to one side of the connection and the ground to the other side. The plate the socket (3-pin round type) is mounted on has several switches, and I only have power (12 VDC) at the socket when the "Charge/Run" switch is on "Charge". The way I currently have the power wires connected to the foot pedal the motor works, but I have no control. When I flip the switch to "charge" the motor turns on and the prop spins. The switch on the pedal and the speed/off rheostat does nothing.
I don't know if this is applicable, but when I remove the cover from the top of the trolling motor I see the wires that go down the shaft to power the motor. When I check continuity on these wires they check shorted. Since this is a motor I assume it should check that way. Is that correct?

I have some misc. problems with how the switch plate has been wired (rigged throughout the years) and I can correct these issues, but I don't understand what I'm doing wrong to have no control on the pedal. Is the rheostat bad? Can I disable it and make the foot switch full throttle only? I have attached pictures for reference.

 

[glenn property of pam]

Re: Mercury Thruster Trolling Motor w/ Foot Pedal Questions

it looks like you have wired the plug directly to the motor so when you get power at the plug the trolling motor spins. There should be a terminal before the switch (i bolted mine down but i think its incoming to switch then to rheostat then to the terminal that connects to the trolling motor)

when using 12v only keep switch in the charge position

The trolling motor will read shorted on a ohm meter as you are reading the coils.

 

[wes8313]

Re: Mercury Thruster Trolling Motor w/ Foot Pedal Questions

OK I see your point with the wires being connected directly to the motor. Makes perfect sense.

I have moved the hot wire to the screw next to the motor hot wire screw, and I have continuity on that screw when the button on the pedal is pressed. Everything looks correct now, but the motor does not spin, and when I press the button on the pedal my voltage drops to 0 VDC. It's acting like it's dead shorted. When I release the button the meter jumps back up to 12.8 VDC.

I have noticed, even when it was wired the wrong way (direct to the motor) that sometimes it did this, sometimes the motor would spin. Now it is always "grounding out" and has not spun while hooked up the current way.

Is the trolling motor bad? I have attached a picture of the wiring as it currently is.

 

[glenn property of pam]

Re: Mercury Thruster Trolling Motor w/ Foot Pedal Questions

the voltage drops to 0 volts on the wire coming in to the trolling peddle or the wire going out?
plus why does the ground lead look like it should be one screw over not directly connected?

If the wires are correct (check the ground) then it might be a bad connection in the switch or speed control thats not allowing the power to go through. Try working the switch and turning the speed control back and forth to clean the tips of the contacts

If the input wire is dropping to 0v then look for a poor connection as a dead short could not pull a battery down to 0v before you could see and smell alot of smoke. (make sure the positive lead has a fuse or breaker just in case it is shorted)

if you can get power to the motor (kinda hard to see its shorted as you had it running but it does happen) then try to flick the prop to see if it will spin. (motors need major power to get them started, they require less power once they are turning)

 

[wes8313]

Re: Mercury Thruster Trolling Motor w/ Foot Pedal Questions

***UPDATE***

OK, here's where I am with this thing...

As of today, when I connect the motor to the 12V wiring the motor spins. If I connect it through the switch it does not spin, and it shorts out the 12V wire coming in. My volt meter drops to 0V. As soon as I release the switch the voltage jumps back to 12V.

Normally I'd just say the switch is bad, but according to my meter the switch is functioning. If I check continuity between the two positive screws(1 for motor, 1 for incoming power) they are open until I press the switch, then the two screws are shorted together to allow the voltage to go to the motor. This tells me the switch is fine....but it doesn't work! :mad-new:

As for the question about the ground wire looking like it should go on the screw next to the ground from the motor, I'm not sure. This screw was missing when I got the boat. It doesn't seem to do anything. It doesn't have continuity with anything whether the switch is pressed or not. When I connect either the hot or ground wire to this position the motor does nothing, and nothing is shorted.

Anyone have any ideas??

 

[glenn property of pam]

Re: Mercury Thruster Trolling Motor w/ Foot Pedal Questions

you have power until you close the switch then it drops to zero. that sounds like a bad connection. try cleaning the terminals of the trolling plug and make sure the battery connection is clean and tight. If the corrosion is in the switch it may have to be replaced. (jumping the switch out will tell you if that is the problem)

 

[gary914]

Hi I am having the same problem as Wes8313 replaced wires on the foot pedal due to wear and now it won't work. Anyone have a good picture of a working Mercury thruster plus foot pedal wiring on the bottom of the foot pedal? Just want to know if I have it wrong. The pictures in the post are of Wes8313 post wiring redo and may not be correct, as the post did not say if he ever got it fixed. Just would like to see what a working 12 v. foot pedal wiring looks like the only numbers I can find on the foot pedal is 88308 on the underneath of the actual pedal and 88310 on mounting base. It is problem a late 80's model. Thanks

 

[GA_Boater]

Hi I am having the same problem as Wes8313 replaced wires on the foot pedal due to wear and now it won't work. Anyone have a good picture of a working Mercury thruster plus foot pedal wiring on the bottom of the foot pedal? Just want to know if I have it wrong. The pictures in the post are of Wes8313 post wiring redo and may not be correct, as the post did not say if he ever got it fixed. Just would like to see what a working 12 v. foot pedal wiring looks like the only numbers I can find on the foot pedal is 88308 on the underneath of the actual pedal and 88310 on mounting base. It is problem a late 80's model. Thanks

You are not having the same problem unless you got hold of wes8313's TM. Click on the Forum Help link in the sig below and start a new thread of your own. Thanks.