After I installed a 30" 180W light bar on my boat it has been killing the battery pretty quick. Took a few trips to start doing this though. Last two hunts I've wound up with a dead battery and had to be jumped off last time. Today after the run to the ramp it was dead.
This morning was at most a ten minute boat ride at full throttle with the light on. Boat cranked up fine when heading back to the ramp and then wouldn't start to put it on the trailer. Light was off on the way back obviously.
I'm thinking this is a bad stator ?
How hard is that to replace?
Something is draining the battery while the boat is running and it doesn't seem to make sense. This was never a problem until I put the light bar on.


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I doubt it's your light bar being they hardly pull any amps. Sounds like you have problems else where


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Sounds like a weak cell in the battery to me. Sometimes depending on which cell is weak the battery will draw down quickly but if you let it sit it will come back up on its own.

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I'd start by getting a load tester and checking your battery

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What gauge cable are you running for electrical?

Since this started with you connecting your light, disconnect your light to see if it stops killing your battery.

There may be a short in the light or in your wiring.....

Check the connections on the backside of your ignition switch and make sure they are all clean and tight. I had the same problem and it was coming from a blackened terminal on the back of key switch, sounds like you aren't getting charge. I doubt it's the stator, more likely the voltage regulator or bad connection

I had an issue with my motor not charging the battery while running and it draining out within a run or two. I re ran with 4gauge and it fixed my issue.

Yep my wire from battery to motor had to be changed out to 4 gauge

New. I noticed it wasn't really charging when I'd run. I have a bunch of electronics wired so I use a lot of power from the batteries and without them charging while running that's a problem. My hunting area is almost 30miles from the ramp

What size boat is it? My batteries are up front and having a 1750 w hunt deck using 8gauge wasn't enough because of the distance from the engine to batteries to carry the proper current to charge the batteries.

Having a deep cycle would help. I never skimp on batteries. I'd rather have to replace every few years vs every year

OP didn't indicate the type of motor or stator, this info is specific to a 35HP briggs. Check the voltage at the battery- should be ~12.7V, turn the motor on and for a 20A stator, at about 2000RPM, it should start charging and at about 3500RPM you should see over 14V at the battery terminals. If you have a 50A stator, it will start charging at idle and get up to 14+V as the RPM increases. Check your connections, if you have loose or corroded cable connections at the battery or motor, the battery cables are usually hot to touch when you start the motor.

You can also use your voltmeter to check the AMP draw from the new lights you installed. I have seen lights with defective transformers draw constant current even when the light is off- in the cases I have seen the transformer is very hot to touch. As mentioned above, you can disconnect the light and see if you see a difference after checking that the motor is putting out the voltage to charge the battery.

If the motor is not charging the battery, the Voltage Regulator is the most common cause. If the battery cables have ever been connected backwards, it will toast the VR. BoatDr has posted the procedure to test the Stator AC output and VR in the past. The 20A VR red DC output goes into the wire harness up to the thru the key switch and then routes back to the starter post, you can test the Red output wire for voltage. On the 50A stator, the red DC output connects directly to the starter post.

The stator is behind the flywheel. Its a fixed ring of coils which produce voltage when the magnets in the inner ring of the flywheel rotates past those coils. I have replaced two 20A stators this year that had a washer drop back behind the flywheel that shorted the stator coils. If you pull the flywheel, the coils on the 20A stator should be bright copper colored, the 50A seems to have a lacquer on them. If the coils have been shorted, they will look dark / burnt. In both cases I encountered this year with shorted stators, the VR was still good when the stator was replaced.

Start out working with a voltmeter to see whats going on. Hope this helps.

50A stator:


20A stator- bright copper colored coils:

Thanks guys. I haven't had time to start tracking down what's going on yet but I charged my battery last night and unhooked my light this morning and ran the river with the moon light. Boat cranked every time. I even stopped and turned around to help some guys in a small outboard rig that I accidentally washed up on top of a rock. I shut the boat on and off several times doing that. Must be a short in my wiring maybe?


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Sounds like you have a short in the light