Trolling motor issue

[DLD24]

I will go out with a fully charged battery and after 2 or 3 hours it will start acting like the battery is dead and the motor will say it needs charging...I hook up the battery to the charger and it says its still 70%...It did this with my buddies battery also so I'm pretty sure its the motor not the battery...Anyone have any idea what the problem could be?? Its a older  powerdrive 

[h8go4s]

What is the make, model, thrust and voltage of the trolling motor? What type of battery, what size, what is the reserve capacity of the battery, how old is it, is the water level correct? Check the battery voltage with a multimeter both at the battery posts and at the trolling motor plug.

[jramsber]

I had a similar problem. Check for corrosion at your connections. Use some anti corrosion grease and/or spray. I can't remember the name of the product that I used but it worked great. 

[Rick G]

Corrosion  would be the first thing I would check for.  Go through and inspect all your wiring, from the battery connections to the trolling motor plug. Look for any cracks in the wires themself,  cracks will let small amounts of moisture in witch will cause corrision over time. 

[gunner55]

I keep a tube of di-electric grease along with a small bottle of distilled ware in our tool box in the boat.The grease is a little spendy but works great & worth it when it comes to eliminating batteries issues.

[mojoputter]

Measure the voltage on the batteries when you have a load on it, run the motor and take a measure, if it doesn't drop when its running then it would be something with the motor, or something from the batteries to the motor.

[BobT]

Verify the electrolyte level in the battery too.  It should be filled to the bottom of the tubes (about 1/2" from top of battery).  If you need to add, use distilled water.  Tap water or any other water will contain other inert particles that can contaminate a battery.  

Mojoputter's right on with the voltage check.  Even a weak battery may test at normal voltage using a voltmeter because the meter doesn't load the battery enough.  It's always best to test them under some load.  

Maybe a load test would also be a good idea.  A load test applies a specific load to the battery to see if it can deliver the current per specifications.  If not, then there's a good chance the battery is on its way out.