NS25C3 charging system check?

[tohatsu9.9guy]

I have a Nissan NS25c3. It is electric start, and after a while of fishing and restarting the motor, the battery will most often go dead. Keep in mind that sometimes this can be blamed on the running the trolling motor, but a lot of the time I haven't even used the trolling motor when the battery is dead and I have to use the pull start to start the engine. I assume that this motor should have a charging system? Is there any way to check to make sure that the charging system is functioning correctly? Maybe unhook the positive cable from the battery and use a multimeter to see if the cable still has 12V? Any help would be greatly appreciated.

 

[tohatsu9.9guy]

Re: NS25C3 charging system check?

Also, how could I check that the yellow and white wires coming from the charging coil under the flywheel are functioning correctly? I guess this would be the best place to start since if no juice is making it to the rectifier, no juice will make it to the battery..

 

[pvanv]

Re: NS25C3 charging system check?

A dead battery is the result of one of two things: either a defective battery (that self-drains), or using more power than you give it. That can be due to a "leak" or "minor short" in the boat wiring, in addition to the deliberate loads, such as radios, sounders, etc.

The 25C3 has a modest 80-watt charging system (about 6 amps at WOT), so if you consume more than 80 watts while running fast, the motor will not keep the battery full. At lower RPM's, the charging system makes a lot less.

The electrical tests for that motor are detailed in the Factory service manual (available from any dealer -- including several forum members... even me), and require the use of a good analog (not digital) ohm meter. Those can help you zero-in on a specific failing part.

For a "go/no-go" check of whether you are charging, you can either 1- connect an ammeter in series with the battery leads (to show whether you are driving amps into the battery), or, 2- for a somewhat cruder, though easier, test, connect an accurate voltmeter at the fully-charged battery (with nothing but the motor connected) (should be over 13 vdc) and then run the motor. Ideally, the voltage should go up to over 14 (maybe over 15)vdc immediately after starting, as power that was used to operate the starter is restored to the battery.

 

[tohatsu9.9guy]

Re: NS25C3 charging system check?

I have a clymer manual, I'll see if it has testing procedures. I'll use my digital multimeter to try the "crude" test that you described. Thanks a ton.

 

[tohatsu9.9guy]

Re: NS25C3 charging system check?

I performed the positive battery terminal test per the Clymer manual. The reading I got with the motor not running was about 12.36, and went up slightly to about 12.45 when the motor was running. If I unhooked the positive cable from the motor and started the motor, with the negative lead of my multimeter still on the neg cable/battery post, with the positive lead on the unhooked positive battery cable, the reading was 14-16 volts. This confirms that voltage is at least getting to the battery. Does this sound like the charging system is in fact working? I'm not exactly sure why I'd see higher voltage with the cable unhooked from the battery vs with the cable connected to the positive terminal of the battery, unless it has to do with the battery sucking up all the excess voltage. Any input or guidance is greatly appreciated.

 

[pvanv]

Re: NS25C3 charging system check?

Try a better battery. 12.36 is nearly dead.