Electric trolling motor has lost power. Please help.

[bmcduffy]

Hi all. I am hoping you can help me out. I have a 16' Tahoe pontoon boat on an urban lake behind my house. The lake is electric only and my boat has a 12 year old Duracraft 67lb thrust motor.

Last week I noticed it was running at about half power. After running around the lake for a few hours I got back to my dock and checked the batteries (it's a 24 volt system running off two 12 volt batteries wired in series.) One of the batteries had a bad cell and was completely dead.

My problem now is I bought a new battery identical to the one that is still good and it still runs about half power even when dialed all the way up. I double checked all my wiring, fuses, and connections and everything is as it should be.

If anyone can help shed some light on this I would greatly appreciate your input.

Best Regards

 

[gm280]

So are you saying that now with the new battery in series with the older battery you have 24 volts output? What does it read when the trolling motor is running full speed? You could have another bad battery... Measuring voltage is one thing, especially without a load. But measure that same voltage with it loaded will give you a much better indication of the real condition of your setup... JMHO!

 

[alldodge]

Hi all. I am hoping you can help me out. I have a 16' Tahoe pontoon boat on an urban lake behind my house. The lake is electric only and my boat has a 12 year old Duracraft 67lb thrust motor.

Last week I noticed it was running at about half power. After running around the lake for a few hours I got back to my dock and checked the batteries (it's a 24 volt system running off two 12 volt batteries wired in series.) One of the batteries had a bad cell and was completely dead.

My problem now is I bought a new battery identical to the one that is still good and it still runs about half power even when dialed all the way up. I double checked all my wiring, fuses, and connections and everything is as it should be.

If anyone can help shed some light on this I would greatly appreciate your input.

Best Regards

:welcome: to iboats

Agree with GM and will add, you never........... really never want to replace just one battery unless the battery being replaced was no more then 6 months old. You already mentioned that the one battery was near dead, which was also killing the other one. Always replace all batteries, it most always works out better

 

[bmcduffy]

Thanks everyone. I really appreciate the input!

 

[bmcduffy]

This afternoon I did a few tests.

First I unplugged shorepower (I have a new ProMariner dual bank charger on-board) Then I tested both battery's at the terminal. They were showing 13.5 volts each. While still tied to the dock I put it in full forward and the voltage dropped .5 volts to 13 volts. So, I cast off and checked it periodically and it stayed at 12.5 volts for almost an hour. The wiring is tight, clean, and short as I can get it because when I first bought the boat six months ago it had way too much lead and was getting major resistance and the motor would shut off at high speed after a few minutes.

So, the wires are good and nothing gets warm, the connections are new and tight. The motor does not get warm at all after sustained cruising at full throttle.

I guess next step will be what papyson advise and check voltage at the motor, under load. I'll post results tomorrow. Thanks again to everyone for your help and support.

 

[bruceb58]

Just so you know, the 13.5V you measured is a surface voltage that will occur right after you take the charger off. A fully charged battery is around 12.6 or 12.7V so you are really getting very little voltage drop at the battery itself.

 

[bmcduffy]

Thank you Bruce. I knew that was normal as was the drop to 12.5V. We took the boat out last night and out of the blue the power ramped back up. I suspect it might be in the speed control on the console. The setup is a toggle switch for forward/neutral/reverse and a knob for speed. The knob is basically a rheostat similar to a light dimmer. I am going to look in there when I get home tonight.

 

[airshot]

Some years back I had an elec trolling motor that developed a speed problem and it turned out to be inside the motor. Mine was a Minkota but the speed coil as it was called developed a short and had to be replaced. It was a wound wire system that fit just inside the tube that holds the motor itself. I called Minkota and they sent me the winding with a set of instructions. The tube came apart and the speed coil slipped inside around the armature, connected the wires, added new O rings and reassembled. Still have the motor to this day and it still runs great.

 

[gm280]

Some years back I had an elec trolling motor that developed a speed problem and it turned out to be inside the motor. Mine was a Minkota but the speed coil as it was called developed a short and had to be replaced. It was a wound wire system that fit just inside the tube that holds the motor itself. I called Minkota and they sent me the winding with a set of instructions. The tube came apart and the speed coil slipped inside around the armature, connected the wires, added new O rings and reassembled. Still have the motor to this day and it still runs great.

Speed coils seem like a bad idea for controlling the speed of any electric motor. Because even though you reduce the speed, it still uses the same amount of current. And that extra current is dissipated in heat...what a waste... There are better ways!

 

[bmcduffy]

I didn't get a chance to look into the speed control last night. Hopefully this weekend. If I can rule that out then I will turn my attention to the motor. Hope you all have a great weekend.

 

[Silvertip]

Speed coils were the only "reasonable and inexpensive" way to control trolling motors years ago just like they were used to control the heater/AC fan motor in your car until more recent years. Electronics have come a long way (as did the prices) so most new trollers are electronically controlled and as a result consume less power. One thing you might do is remove the prop and check for fish line wrapped tightly around the shaft. This can cut the seal and slow the motor if there is enough of the stuff wound up.