12 v/24 v wiring question-old boat

[babymaker]

I have an older boat with older MG trolling 42 lb thrust. I have 2 sets of pos/neg wires going to battery compartment. The motor has a 12 v and 24 volt switch-3 prongs. I was running the motor for about 2 weeks running 24 volts and running a pos and neg to each battery with no jumper cable between the 2 batteries. Motor ran fast and good and then started blowing fuses after 2 weeks. I fiddled with the outlet and now it runs off 1 battery only and with the motor switched to 24 v only but not very fast. When I go back to adding the second battery it blows the fuse on this one but still runs off the other one but only at a slow speed. I don't see any probs/connections with the wiring. With 2 sets of pos/neg wires am I set up for 24 volts? I must have more than an improper hook up just needing some guidance on which way to go. Any help would be greatly appreciated. Thanks.

 

[Nhpatriot]

I would be very surprised if you have a 24v system on your boat. the 2 batteries are just for additional storage but should be wired for 12 v. The sure method to determine the voltage is with a volt meter. Measure where you are connecting your trolling motor for Dc volts.
you should just connect to one battery at a time. If there is a battery selector switch you could connect after that so you can run the motor from either battery.

 

[babymaker]

Thanks. It is pulling 18 volts from each battery . Whenever I try to hook up the second battery, however, with the second set of wires, it gets too hot.
Don't see anything wrong from exterior of any of the wires on this second set but something is wrong. Could it be one of the switches or would it be in this set of wires somewhere?

Also, just wondering why I was able to run off both batteries at such a good speed for a while before everything went south...now I am back to just one battery and one set of wires and a slow speed from 41 lbs thrust motor-nothing wrapped around shaft, etc. Many thanks.

maybe I should just get a 24 v motor and run 2 sets of wires to batteries and use a jump wire?

 

[Silvertip]

You are not pulling 18 volts from each battery. If that were true you would have a 36 volt system which you don't. Batteries provide 12.6 volts period. Ain't possible to get 18 volts from a 12 volt battery. The only why you can get 18 volts is have one good battery (12 volts) and one bad battery (6 volts). 12+6=18 where I went to school. So where and how are you measuring this 18 volts. First issue I see is you have four wires (two red/black pairs) going up front but you have a three pin trolling motor connector. Does the panel on which the trolling motor receptacle have a switch labeled 12/24/RUN/CHARGE?? And just so you know, you do not use a jumper wire at the batteries in a four wire system. You need to provide some pictures and/or more detail about your boat. You need to help us understand what you have so we can help you. If you get a 24 volt ONLY motor you do not need four wires. You only need two and the jumper wire. You can use four but why. It isn't necessary.