View Full Version : Electric trolling motor has lost power.

02-10-2015, 06:32 PM
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

02-11-2015, 08:59 AM
note..you have to have the motor on and running to measure the voltage because you are looking for a voltage drop and will read battery output everywhere without it..i would first read the battery output with the motor off and then on at the battery itself....i would expect a slight drop when the motor is on...but less than a volt...the 2nd test point should be at the motor itself after all the connections or plugs etc...you may be able to remove the cover and get to a place to measure..if not you may have to skin some wires just enough to get the meter leads to make contact..you should read the same as you do at the battery post...if you dont then you have a bad connection or something in the wiring...if you get the same reading you will have to get deeper into the motor wiring itself....

while i was typing this i thought of something else..remove the prop and make sure you dont have a load of mono filament fishing line wrapped around the shaft...

make sure when you replaced the battery you have them in series and not parallel...

02-11-2015, 07:28 PM
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.

02-12-2015, 09:29 PM
you should be reading in excess of 24 volts between the two posts that the trolling motor is connected to...