24V Trolling Motor Only Working on 12V

I just picked up a new to me ProCraft 200 Combo tonight and it has a factory installed Motorguide 12/24V trolling motor. When I first looked at the boat, I thought I remembered the PO demoing that the trolling motor worked fine, and then when we went for a sea trial yesterday it would only work on 12V and turn very slowly. It has a 12/off/24v switch on the foot pedal. He thought it might be that one of the batteries was dead, but when I got the boat home tonight and checked it out I found that both batteries are showing 12.9V so that isn't the problem. I can probably eventually figure out how to trace this out, but I thought I'd ask here first. It has a four prong plug in the bow... what should be the voltage on the prongs? Assuming the voltage there is correct, what else might I want to check to diagnose this. The wiring is exposed under the pedal and there is the basic speed dial, on/off pedal, and the three position switch, so I could check those but not sure what I should be seeing on them. Any help would be appreciated... would like to break her in fishing on Saturday.

Re: 24V Trolling Motor Only Working on 12V

There are three wire and four wire troller battery wiring systems for 12/24 volt systems. A three wire system is a simple system where two batteries are connected in series. 24 volts is measured across the ground from the first battery and positive of the second. Those to wires go to the plug which may be either a three or four terminal. 12 volts for that system adds the third wire from the POS of the first battery and that terminates at another terminal on the troller plug. So you have three wires using three terminals.

A four wire system has separate pairs of wires from each battery going to the troller plug. The troller plug must have four terminals. You won't measure 24 volts anywhere on that receptacle because you have two separate 12 volt circuits feeding it. The 12 volt setting on your foot pedal PARALLELS the two batteries for 12 volt operation. The 24 volt setting puts the batteries in series.

That's the best I can do for you since we have no idea which system you have.

Re: 24V Trolling Motor Only Working on 12V

Thanks for the quick info Silvertip. I did go back out and fiddle some more and found the following:

- I have a four wire receptacle at the bow.
- There are no switches on the bow panel, just the receptacle.
- The plug going into the receptacle has four prongs, but only 3 wires - Red, Orange, and Black.
- I didn't take the panel apart to see what was on the back of it for wires yet.
- In the battery compartment, I have two batteries that each have black and red wires going to them.
- I then found two 40 amp fuses there and one of them was blown.

I replaced the fuse and the motor now works on 12V or 24V. When on 24V it spins really fast... full strength. When on 12V it spins really slowly. Is this normal? I am assuming this lets you have lower speed fine control for really calm water??? Or, is it not working right.

The trolling motor is a Motorguide 50# 12/24V ... I believe it said Brute, Model 750.

So its working now, but I'm not sure if its working the way it should be. Thanks again... you are the master of trolling motor systems for sure!

Re: 24V Trolling Motor Only Working on 12V

I see that you've got it figured out. But for others that may have the same wiring question, here's a link that helped me out.

http://www.marinco.com/files/support/products/manuals/200929.pdf

Re: 24V Trolling Motor Only Working on 12V

Good reference but that is missing the four wire system I just described. The Marinco document shows the negative posts of the two batteries tied together at the batteries. A four wire system runs a separate pair of wires from each battery directly to the receptacle. If you notice, the 12/24 Marinco system still has only three wires.

Re: 24V Trolling Motor Only Working on 12V

Hey Silvertip... thanks for the info. I had another question in there that got lost. The trolling motor runs full speed on 24V, and much slower on 12V. Is that normal with a 12/24V trolling motor?

Re: 24V Trolling Motor Only Working on 12V

Thats why they gave you the option. If the motor ran as fast on 12 volts as it did on 24 there would be no need for a 24 volt capability.