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Jeff G.
Jeff G., Marine Mechanic
Category: Boat
Satisfied Customers: 4728
Experience:  42 years experience, Certified Master Technician, All Major Outboards, Sterndrives, Hi-Performance
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i have a yamaha 115txrc four stroke outboard that is not charging

Resolved Question:

i have a yamaha 115txrc four stroke outboard that is not charging the battery .
I have replaced the battery(high quality interstate marine battery) and it runs down in 5-8
hours of run time.
I have checked for any loose or corroded connections and have found none.
The battery measured 12 volts dc before starting the engine.
After starting the engine, the voltage varies between 9.5 to 12.7. I have understood it should be at 13 volts when the engine is running.
One person said it could be a fried voltage regulator and to take the regulator loose and look athe back to see if its charred.
I did take loose and checked the back but it looks normal.
thoughts on what to test next or what the problem might be?
Submitted: 7 years ago.
Category: Boat
Expert:  Jeff G. replied 7 years ago.
I will be happy to assist you. If you have a question or need clarification please post back at any time.
A fully charged battery at rest measures about 12.5 volts. You should be charging 13.5+. So by showing you are at 9.5 to 12.7 you are not charging.
You have a rectifier/regulator system. In almost all cases that is the problem. There are only two parts to your charging system the stator which is a series of coils under the flywheel and the rectifier/regulator.
Disconnect the battery.

To test the stator you will need an ohm meter. Set it to the 1 scale.
Disconnect the stator harness from the rectifier in the front of the engine.
Test from each of the green wires from the stator. Mark each green wire #1,2,3.
Test from #1 to #2 then from #1 to #3 then from #2 to #3 the reading should be .2 to .8 ohms. If not the stator is bad.
If the stator checks bad then the rectifier is probably OK but to check it check the green wires on the rectifier side of the harness; Put your meter to the 10 scale, put the red lead on the red wire of the rectifier then the black meter lead to each of the green wires one at a time, you should read 100-300 ohms. Now put the meter's black lead to the red wire and the red meter to each of the green wires and you should not get a reading.

These resistance tests should tell you if the problem is the stator or the rectifier/regulator.
Customer: replied 7 years ago.

How do i identify the stator and the rectifier side of the harness?

there are four wires in the harness, three have a white wrapping and one red wire.


Also how do i release the stator harness? i see a release on the plug but i dont know how to release it?



Expert:  Jeff G. replied 7 years ago.
Push in and down on the tab on the connector. Pull the connector apart. On yours you may have white instead of green wires but the tests are the same. The rectifier side is connected to the rectifier which is on the front of the engine,
Here is a drawing of the rectifier #14

Customer: replied 7 years ago.

the stator checks bad. not sure how to test the rectifier. It doesn't make sense to me that you can check the rectifier by checking the wires in the harness when the rectifier is not in the circuit. What am I missing?

Expert:  Jeff G. replied 7 years ago.
Yamaha uses a test harness between the rectifier and engine harness, you just check the pins in the rectifier where the harness connects. Sorry I wasn't clear
Customer: replied 7 years ago.

I pulled the rectifier out and checked it like you specified. With the red lead on the red wire, I get a reading about 230 or so for each of the other connections. But when I check with the black probe on the red wire, I do get a reading on each of the other 3 connections - about 210 on each. (You said I should NOT get one, right? ) That means I have a bad rectifier, correct?


If that's the case, where would you recommend getting a new one? Is there somewhere safe online to buy or should I get from my local yamaha dealer?



Expert:  Jeff G. replied 7 years ago.
Correct, the rectifier should test one way and not the other. A good place would be they are dependable, discount and sell OEM parts.
Customer: replied 7 years ago.
One more thing - can you give me a rough estimate of what a typical boat shop would have cost to get this thing diagnosed? Really appreciate your help!
Expert:  Jeff G. replied 7 years ago.
About 1 1/2 hours X the hourly rate of probably $90 for a dealer about $135.00 plus parts.
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